diff --git a/lib/Slic3r/GUI/3DScene.pm b/lib/Slic3r/GUI/3DScene.pm
index 7f2fe4346..f9e9e668d 100644
--- a/lib/Slic3r/GUI/3DScene.pm
+++ b/lib/Slic3r/GUI/3DScene.pm
@@ -2044,4 +2044,11 @@ sub reset_legend_texture {
     Slic3r::GUI::_3DScene::reset_legend_texture();
 }
 
+sub get_current_print_zs {
+    my ($self) = @_;
+    
+    my $count = $self->volumes->get_current_print_zs();
+    return $count;
+}
+
 1;
diff --git a/lib/Slic3r/GUI/Plater/3DPreview.pm b/lib/Slic3r/GUI/Plater/3DPreview.pm
index 554b9e35a..a8bda3e50 100644
--- a/lib/Slic3r/GUI/Plater/3DPreview.pm
+++ b/lib/Slic3r/GUI/Plater/3DPreview.pm
@@ -74,12 +74,8 @@ sub new {
     
     my $combochecklist_features = $self->{combochecklist_features} = Wx::ComboCtrl->new();
     $combochecklist_features->Create($self, -1, "Feature types", wxDefaultPosition, [200, -1], wxCB_READONLY);
-    #FIXME If the following line is removed, the combo box popup list will not react to mouse clicks.
-    # On the other side, with this line the combo box popup cannot be closed by clicking on the combo button on Windows 10.
-    $combochecklist_features->UseAltPopupWindow();
-    $combochecklist_features->EnablePopupAnimation(0);
     my $feature_text = "Feature types";
-    my $feature_items = "Perimeter|External perimeter|Overhang perimeter|Internal infill|Solid infill|Top solid infill|Bridge infill|Gap fill|Skirt|Support material|Support material interface|Wipe tower";
+    my $feature_items = "Perimeter|External perimeter|Overhang perimeter|Internal infill|Solid infill|Top solid infill|Bridge infill|Gap fill|Skirt|Support material|Support material interface|Wipe tower|Custom";
     Slic3r::GUI::create_combochecklist($combochecklist_features, $feature_text, $feature_items, 1);
     
     my $checkbox_travel         = $self->{checkbox_travel}          = Wx::CheckBox->new($self, -1, "Travel");
@@ -255,6 +251,7 @@ sub new {
                                     'Support material'           => '00FF00',
                                     'Support material interface' => '008000',
                                     'Wipe tower'                 => 'B3E3AB',
+                                    'Custom'                     => 'FFFF00',
                                  );
     $self->gcode_preview_data->set_extrusion_paths_colors(\@extrusion_roles_colors);
     
@@ -322,31 +319,9 @@ sub load_print {
         return;
     }
     
-    my $z_idx_low = $self->slider_low->GetValue;
-    my $z_idx_high = $self->slider_high->GetValue;
-    $self->enabled(1);
-    $self->slider_low->SetRange(0, $n_layers - 1);
-    $self->slider_high->SetRange(0, $n_layers - 1);
-    if ($z_idx_high < $n_layers && ($self->single_layer || $z_idx_high != 0)) {
-        # use $z_idx
-    } else {
-        # Out of range. Disable 'single layer' view.
-        $self->single_layer(0);
-        $self->{checkbox_singlelayer}->SetValue(0);
-        $z_idx_low = 0;
-        $z_idx_high = $n_layers - 1;
-    }
-    if ($self->single_layer) {
-        $z_idx_low = $z_idx_high;
-    } elsif ($z_idx_low > $z_idx_high) {
-        $z_idx_low = 0;
-    }
-    $self->slider_low->SetValue($z_idx_low);
-    $self->slider_high->SetValue($z_idx_high);
-    $self->slider_low->Show;
-    $self->slider_high->Show;
-    $self->Layout;
-
+    # used to set the sliders to the extremes of the current zs range
+    $self->{force_sliders_full_range} = 0;
+    
     if ($self->{preferred_color_mode} eq 'tool_or_feature') {
         # It is left to Slic3r to decide whether the print shall be colored by the tool or by the feature.
         # Color by feature if it is a single extruder print.
@@ -384,16 +359,58 @@ sub load_print {
             }
             $self->show_hide_ui_elements('simple');
         } else {
+            $self->{force_sliders_full_range} = (scalar(@{$self->canvas->volumes}) == 0) && $self->auto_zoom;
             $self->canvas->load_gcode_preview($self->print, $self->gcode_preview_data, \@colors);
             $self->show_hide_ui_elements('full');
+
+            # recalculates zs and update sliders accordingly
+            $self->{layers_z} = $self->canvas->get_current_print_zs();
+            $n_layers = scalar(@{$self->{layers_z}});            
         }
+
+        $self->update_sliders($n_layers);
+                
         if ($self->auto_zoom) {
             $self->canvas->zoom_to_volumes;
         }
         $self->_loaded(1);
     }
+}
+
+sub update_sliders
+{
+    my ($self, $n_layers) = @_;
+        
+    my $z_idx_low = $self->slider_low->GetValue;
+    my $z_idx_high = $self->slider_high->GetValue;
+    $self->enabled(1);
+    $self->slider_low->SetRange(0, $n_layers - 1);
+    $self->slider_high->SetRange(0, $n_layers - 1);
     
+    if ($self->{force_sliders_full_range}) {
+        $z_idx_low = 0;
+        $z_idx_high = $n_layers - 1;
+    } elsif ($z_idx_high < $n_layers && ($self->single_layer || $z_idx_high != 0)) {
+        # use $z_idx
+    } else {
+        # Out of range. Disable 'single layer' view.
+        $self->single_layer(0);
+        $self->{checkbox_singlelayer}->SetValue(0);
+        $z_idx_low = 0;
+        $z_idx_high = $n_layers - 1;
+    }
+    if ($self->single_layer) {
+        $z_idx_low = $z_idx_high;
+    } elsif ($z_idx_low > $z_idx_high) {
+        $z_idx_low = 0;
+    }
+    
+    $self->slider_low->SetValue($z_idx_low);
+    $self->slider_high->SetValue($z_idx_high);
+    $self->slider_low->Show;
+    $self->slider_high->Show;
     $self->set_z_range($self->{layers_z}[$z_idx_low], $self->{layers_z}[$z_idx_high]);
+    $self->Layout;    
 }
 
 sub set_z_range
diff --git a/xs/src/libslic3r/ExtrusionEntity.hpp b/xs/src/libslic3r/ExtrusionEntity.hpp
index f5e243419..16ef51c1f 100644
--- a/xs/src/libslic3r/ExtrusionEntity.hpp
+++ b/xs/src/libslic3r/ExtrusionEntity.hpp
@@ -26,6 +26,7 @@ enum ExtrusionRole {
     erSupportMaterial,
     erSupportMaterialInterface,
     erWipeTower,
+    erCustom,
     // Extrusion role for a collection with multiple extrusion roles.
     erMixed,
 };
diff --git a/xs/src/libslic3r/GCode.cpp b/xs/src/libslic3r/GCode.cpp
index 2c2df6ec3..28c03ba2c 100644
--- a/xs/src/libslic3r/GCode.cpp
+++ b/xs/src/libslic3r/GCode.cpp
@@ -587,6 +587,15 @@ void GCode::_do_export(Print &print, FILE *file, GCodePreviewData *preview_data)
     this->_print_first_layer_bed_temperature(file, print, start_gcode, initial_extruder_id, true);
     // Set extruder(s) temperature before and after start G-code.
     this->_print_first_layer_extruder_temperatures(file, print, start_gcode, initial_extruder_id, false);
+
+    if (m_enable_analyzer)
+    {
+        // adds tag for analyzer
+        char buf[32];
+        sprintf(buf, ";%s%d\n", GCodeAnalyzer::Extrusion_Role_Tag.c_str(), erCustom);
+        _writeln(file, buf);
+    }
+
     // Write the custom start G-code
     _writeln(file, start_gcode);
     // Process filament-specific gcode in extruder order.
@@ -770,6 +779,15 @@ void GCode::_do_export(Print &print, FILE *file, GCodePreviewData *preview_data)
     // Write end commands to file.
     _write(file, this->retract());
     _write(file, m_writer.set_fan(false));
+
+    if (m_enable_analyzer)
+    {
+        // adds tag for analyzer
+        char buf[32];
+        sprintf(buf, ";%s%d\n", GCodeAnalyzer::Extrusion_Role_Tag.c_str(), erCustom);
+        _writeln(file, buf);
+    }
+
     // Process filament-specific gcode in extruder order.
     if (print.config.single_extruder_multi_material) {
         // Process the end_filament_gcode for the active filament only.
diff --git a/xs/src/libslic3r/GCode/Analyzer.cpp b/xs/src/libslic3r/GCode/Analyzer.cpp
index f8d196f23..6530806c4 100644
--- a/xs/src/libslic3r/GCode/Analyzer.cpp
+++ b/xs/src/libslic3r/GCode/Analyzer.cpp
@@ -150,7 +150,13 @@ void GCodeAnalyzer::_process_gcode_line(GCodeReader&, const GCodeReader::GCodeLi
 {
     // processes 'special' comments contained in line
     if (_process_tags(line))
+    {
+#if 0
+        // DEBUG ONLY: puts the line back into the gcode
+        m_process_output += line.raw() + "\n";
+#endif
         return;
+    }
 
     // sets new start position/extrusion
     _set_start_position(_get_end_position());
diff --git a/xs/src/libslic3r/GCode/PreviewData.cpp b/xs/src/libslic3r/GCode/PreviewData.cpp
index 5a23d332d..183e10b2a 100644
--- a/xs/src/libslic3r/GCode/PreviewData.cpp
+++ b/xs/src/libslic3r/GCode/PreviewData.cpp
@@ -125,6 +125,7 @@ const GCodePreviewData::Color GCodePreviewData::Extrusion::Default_Extrusion_Rol
     Color(0.0f, 0.5f, 0.0f, 1.0f),   // erSupportMaterial
     Color(0.0f, 0.0f, 0.5f, 1.0f),   // erSupportMaterialInterface
     Color(0.7f, 0.89f, 0.67f, 1.0f), // erWipeTower
+    Color(1.0f, 1.0f, 0.0f, 1.0f),   // erCustom
     Color(0.0f, 0.0f, 0.0f, 1.0f)    // erMixed
 };
 
@@ -144,6 +145,7 @@ const std::string GCodePreviewData::Extrusion::Default_Extrusion_Role_Names[Num_
     "Support material",
     "Support material interface",
     "Wipe tower",
+    "Custom",
     "Mixed"
 };
 
@@ -360,8 +362,11 @@ GCodePreviewData::LegendItemsList GCodePreviewData::get_legend_items(const std::
     {
     case Extrusion::FeatureType:
         {
-            items.reserve(erMixed - erPerimeter + 1);
-            for (unsigned int i = (unsigned int)erPerimeter; i < (unsigned int)erMixed; ++i)
+            ExtrusionRole first_valid = erPerimeter;
+            ExtrusionRole last_valid = erCustom;
+
+            items.reserve(last_valid - first_valid + 1);
+            for (unsigned int i = (unsigned int)first_valid; i <= (unsigned int)last_valid; ++i)
             {
                 items.emplace_back(extrusion.role_names[i], extrusion.role_colors[i]);
             }
diff --git a/xs/src/slic3r/GUI/3DScene.cpp b/xs/src/slic3r/GUI/3DScene.cpp
index 3a8aa5ca7..f492ed342 100644
--- a/xs/src/slic3r/GUI/3DScene.cpp
+++ b/xs/src/slic3r/GUI/3DScene.cpp
@@ -450,6 +450,25 @@ void GLVolumeCollection::render_legacy() const
     glDisableClientState(GL_NORMAL_ARRAY);
 }
 
+std::vector<double> GLVolumeCollection::get_current_print_zs() const
+{
+    std::vector<double> print_zs;
+
+    for (GLVolume *vol : this->volumes)
+    {
+        for (coordf_t z : vol->print_zs)
+        {
+            double round_z = (double)round(z * 100000.0f) / 100000.0f;
+            if (std::find(print_zs.begin(), print_zs.end(), round_z) == print_zs.end())
+                print_zs.push_back(round_z);
+        }
+    }
+
+    std::sort(print_zs.begin(), print_zs.end());
+
+    return print_zs;
+}
+
 // caller is responsible for supplying NO lines with zero length
 static void thick_lines_to_indexed_vertex_array(
     const Lines                 &lines, 
@@ -2205,6 +2224,9 @@ void _3DScene::_update_gcode_volumes_visibility(const GCodePreviewData& preview_
             {
             case GCodePreviewVolumeIndex::Extrusion:
                 {
+                    if ((ExtrusionRole)s_gcode_preview_volume_index.first_volumes[i].flag == erCustom)
+                        volume->zoom_to_volumes = false;
+                    
                     volume->is_active = preview_data.extrusion.is_role_flag_set((ExtrusionRole)s_gcode_preview_volume_index.first_volumes[i].flag);
                     break;
                 }
diff --git a/xs/src/slic3r/GUI/3DScene.hpp b/xs/src/slic3r/GUI/3DScene.hpp
index 542be3ef6..3e26bf6d3 100644
--- a/xs/src/slic3r/GUI/3DScene.hpp
+++ b/xs/src/slic3r/GUI/3DScene.hpp
@@ -372,6 +372,9 @@ public:
 
     void set_render_interleaved_only_volumes(const RenderInterleavedOnlyVolumes& render_interleaved_only_volumes) { _render_interleaved_only_volumes = render_interleaved_only_volumes; }
 
+    // Returns a vector containing the sorted list of all the print_zs of the volumes contained in this collection
+    std::vector<double> get_current_print_zs() const;
+
 private:
     GLVolumeCollection(const GLVolumeCollection &other);
     GLVolumeCollection& operator=(const GLVolumeCollection &);
diff --git a/xs/src/slic3r/GUI/GUI.cpp b/xs/src/slic3r/GUI/GUI.cpp
index 0d7d58e0f..0b122453f 100644
--- a/xs/src/slic3r/GUI/GUI.cpp
+++ b/xs/src/slic3r/GUI/GUI.cpp
@@ -487,10 +487,17 @@ void create_combochecklist(wxComboCtrl* comboCtrl, std::string text, std::string
     wxCheckListBoxComboPopup* popup = new wxCheckListBoxComboPopup;
     if (popup != nullptr)
     {
+        // FIXME If the following line is removed, the combo box popup list will not react to mouse clicks.
+        //  On the other side, with this line the combo box popup cannot be closed by clicking on the combo button on Windows 10.
+        comboCtrl->UseAltPopupWindow();
+
+        comboCtrl->EnablePopupAnimation(false);
         comboCtrl->SetPopupControl(popup);
         popup->SetStringValue(text);
-        popup->Connect(wxID_ANY, wxEVT_CHECKLISTBOX, wxCommandEventHandler(wxCheckListBoxComboPopup::OnCheckListBox), nullptr, popup);
-        popup->Connect(wxID_ANY, wxEVT_LISTBOX, wxCommandEventHandler(wxCheckListBoxComboPopup::OnListBoxSelection), nullptr, popup);
+        popup->Bind(wxEVT_CHECKLISTBOX, [popup](wxCommandEvent& evt) { popup->OnCheckListBox(evt); });
+        popup->Bind(wxEVT_LISTBOX, [popup](wxCommandEvent& evt) { popup->OnListBoxSelection(evt); });
+        popup->Bind(wxEVT_KEY_DOWN, [popup](wxKeyEvent& evt) { popup->OnKeyEvent(evt); });
+        popup->Bind(wxEVT_KEY_UP, [popup](wxKeyEvent& evt) { popup->OnKeyEvent(evt); });
 
         std::vector<std::string> items_str;
         boost::split(items_str, items, boost::is_any_of("|"), boost::token_compress_off);
diff --git a/xs/src/slic3r/GUI/wxExtensions.cpp b/xs/src/slic3r/GUI/wxExtensions.cpp
index b5f0595f8..1ebd7979e 100644
--- a/xs/src/slic3r/GUI/wxExtensions.cpp
+++ b/xs/src/slic3r/GUI/wxExtensions.cpp
@@ -1,6 +1,8 @@
 #include "wxExtensions.hpp"
 
-const unsigned int wxCheckListBoxComboPopup::Height = 210;
+const unsigned int wxCheckListBoxComboPopup::DefaultWidth = 200;
+const unsigned int wxCheckListBoxComboPopup::DefaultHeight = 200;
+const unsigned int wxCheckListBoxComboPopup::DefaultItemHeight = 18;
 
 bool wxCheckListBoxComboPopup::Create(wxWindow* parent)
 {
@@ -25,16 +27,55 @@ wxString wxCheckListBoxComboPopup::GetStringValue() const
 wxSize wxCheckListBoxComboPopup::GetAdjustedSize(int minWidth, int prefHeight, int maxHeight)
 {
     // matches owner wxComboCtrl's width
+    // and sets height dinamically in dependence of contained items count
 
     wxComboCtrl* cmb = GetComboCtrl();
     if (cmb != nullptr)
     {
         wxSize size = GetComboCtrl()->GetSize();
-        size.SetHeight(Height);
+
+        unsigned int count = GetCount();
+        if (count > 0)
+            size.SetHeight(count * DefaultItemHeight);
+        else
+            size.SetHeight(DefaultHeight);
+
         return size;
     }
     else
-        return wxSize(200, Height);
+        return wxSize(DefaultWidth, DefaultHeight);
+}
+
+void wxCheckListBoxComboPopup::OnKeyEvent(wxKeyEvent& evt)
+{
+    // filters out all the keys which are not working properly
+    switch (evt.GetKeyCode())
+    {
+    case WXK_LEFT:
+    case WXK_UP:
+    case WXK_RIGHT:
+    case WXK_DOWN:
+    case WXK_PAGEUP:
+    case WXK_PAGEDOWN:
+    case WXK_END:
+    case WXK_HOME:
+    case WXK_NUMPAD_LEFT:
+    case WXK_NUMPAD_UP:
+    case WXK_NUMPAD_RIGHT:
+    case WXK_NUMPAD_DOWN:
+    case WXK_NUMPAD_PAGEUP:
+    case WXK_NUMPAD_PAGEDOWN:
+    case WXK_NUMPAD_END:
+    case WXK_NUMPAD_HOME:
+    {
+        break;
+    }
+    default:
+    {
+        evt.Skip();
+        break;
+    }
+    }
 }
 
 void wxCheckListBoxComboPopup::OnCheckListBox(wxCommandEvent& evt)
@@ -48,6 +89,8 @@ void wxCheckListBoxComboPopup::OnCheckListBox(wxCommandEvent& evt)
         event.SetEventObject(cmb);
         cmb->ProcessWindowEvent(event);
     }
+
+    evt.Skip();
 }
 
 void wxCheckListBoxComboPopup::OnListBoxSelection(wxCommandEvent& evt)
diff --git a/xs/src/slic3r/GUI/wxExtensions.hpp b/xs/src/slic3r/GUI/wxExtensions.hpp
index 8e62f766c..e61c17bbc 100644
--- a/xs/src/slic3r/GUI/wxExtensions.hpp
+++ b/xs/src/slic3r/GUI/wxExtensions.hpp
@@ -6,7 +6,9 @@
 
 class wxCheckListBoxComboPopup : public wxCheckListBox, public wxComboPopup
 {
-    static const unsigned int Height;
+    static const unsigned int DefaultWidth;
+    static const unsigned int DefaultHeight;
+    static const unsigned int DefaultItemHeight;
 
     wxString m_text;
 
@@ -17,6 +19,8 @@ public:
     virtual wxString GetStringValue() const;
     virtual wxSize GetAdjustedSize(int minWidth, int prefHeight, int maxHeight);
 
+    virtual void OnKeyEvent(wxKeyEvent& evt);
+
     void OnCheckListBox(wxCommandEvent& evt);
     void OnListBoxSelection(wxCommandEvent& evt);
 };
diff --git a/xs/xsp/GUI_3DScene.xsp b/xs/xsp/GUI_3DScene.xsp
index dbf171615..4670c5c7e 100644
--- a/xs/xsp/GUI_3DScene.xsp
+++ b/xs/xsp/GUI_3DScene.xsp
@@ -85,7 +85,11 @@
 
     int count()
         %code{% RETVAL = THIS->volumes.size(); %};
+        
+    std::vector<double> get_current_print_zs()
+        %code{% RETVAL = THIS->get_current_print_zs(); %};
 
+        
     void set_range(double low, double high);
 
     void render_VBOs() const;