diff --git a/lib/Slic3r/GUI/Plater.pm b/lib/Slic3r/GUI/Plater.pm
index 94f01e25d..d2a7a23b1 100644
--- a/lib/Slic3r/GUI/Plater.pm
+++ b/lib/Slic3r/GUI/Plater.pm
@@ -594,7 +594,7 @@ sub new {
         $self->on_process_completed($event->GetInt ? undef : $event->GetString);
     });
     
-# XXX: ???
+# XXX: not done
     {
         my $timer_id = Wx::NewId();
         $self->{apply_config_timer} = Wx::Timer->new($self, $timer_id);
@@ -1179,7 +1179,7 @@ sub reset {
     $self->update;
 }
 
-# XXX: not done
+# XXX: VK: done
 sub increase {
     my ($self, $copies) = @_;
     $copies //= 1;
@@ -1211,7 +1211,7 @@ sub increase {
     $self->schedule_background_process;
 }
 
-# XXX: not done
+# XXX: VK: done
 sub decrease {
     my ($self, $copies_asked) = @_;
     my $copies = $copies_asked // 1;
@@ -1239,7 +1239,7 @@ sub decrease {
     $self->update;
 }
 
-# XXX: not done
+# XXX: VK: done
 sub set_number_of_copies {
     my ($self) = @_;
     # get current number of copies
@@ -1258,8 +1258,8 @@ sub set_number_of_copies {
     }
 }
 
-# XXX: not done (?)
-sub _get_number_from_user {     # XXX: Enrico
+# XXX: VK: removed
+sub _get_number_from_user {
     my ($self, $title, $prompt_message, $error_message, $default, $only_positive) = @_;
     for (;;) {
         my $value = Wx::GetTextFromUser($prompt_message, $title, $default, $self);
@@ -1457,7 +1457,7 @@ sub changescale {
     $self->update;
 }
 
-# XXX: not done
+# XXX: VK: WIP
 sub arrange {
     my ($self) = @_;
     
@@ -2057,7 +2057,7 @@ sub update {
     $self->Thaw;
 }
 
-# XXX: done in sidebar?
+# XXX: YS: done
 # When a printer technology is changed, the UI needs to be updated to show/hide needed preset combo boxes.
 sub show_preset_comboboxes{
     my ($self, $showSLA) = @_; #if showSLA is oposite value to "ptFFF"
@@ -2076,7 +2076,7 @@ sub show_preset_comboboxes{
     $self->Layout;
 }
 
-# XXX: not done
+# XXX: YS: done
 # When a number of extruders changes, the UI needs to be updated to show a single filament selection combo box per extruder.
 # Also the wxTheApp->{preset_bundle}->filament_presets needs to be resized accordingly
 # and some reasonable default has to be selected for the additional extruders.
@@ -2188,7 +2188,7 @@ sub on_config_change {
     $self->schedule_background_process;
 }
 
-# XXX: not done
+# XXX: YS: WIP
 sub item_changed_selection {
     my ($self, $obj_idx) = @_;
 
@@ -2214,7 +2214,7 @@ sub collect_selections {
     return $selections;
 }
 
-# XXX: not done
+# XXX: YS: done, lambda on LEFT_DOWN
 # Called when clicked on the filament preset combo box.
 # When clicked on the icon, show the color picker.
 sub filament_color_box_lmouse_down
@@ -2268,7 +2268,7 @@ sub filament_color_box_lmouse_down
 #	}
 #}
 
-# XXX: not done
+# XXX: YS: done
 sub changed_object_settings {
     my ($self, $obj_idx, $parts_changed, $part_settings_changed) = @_;
     
@@ -2464,7 +2464,7 @@ sub select_object {
     $self->selection_changed(1);
 }
 
-# XXX: not done
+# XXX: YS: WIP
 sub select_object_from_cpp {
     my ($self, $obj_idx, $vol_idx) = @_;
     
diff --git a/src/libslic3r/Model.cpp b/src/libslic3r/Model.cpp
index 88e4c551a..e0cf14a57 100644
--- a/src/libslic3r/Model.cpp
+++ b/src/libslic3r/Model.cpp
@@ -609,6 +609,15 @@ ModelInstance* ModelObject::add_instance(const ModelInstance &other)
     return i;
 }
 
+ModelInstance* ModelObject::add_instance(const Vec3d &offset, const Vec3d &scaling_factor, const Vec3d &rotation)
+{
+    auto *instance = add_instance();
+    instance->set_offset(offset);
+    instance->set_scaling_factor(scaling_factor);
+    instance->set_rotation(rotation);
+    return instance;
+}
+
 void ModelObject::delete_instance(size_t idx)
 {
     ModelInstancePtrs::iterator i = this->instances.begin() + idx;
diff --git a/src/libslic3r/Model.hpp b/src/libslic3r/Model.hpp
index d9abc109a..695de6127 100644
--- a/src/libslic3r/Model.hpp
+++ b/src/libslic3r/Model.hpp
@@ -96,6 +96,7 @@ public:
 
     ModelInstance* add_instance();
     ModelInstance* add_instance(const ModelInstance &instance);
+    ModelInstance* add_instance(const Vec3d &offset, const Vec3d &scaling_factor, const Vec3d &rotation);
     void delete_instance(size_t idx);
     void delete_last_instance();
     void clear_instances();
diff --git a/src/libslic3r/Print.hpp b/src/libslic3r/Print.hpp
index a646ab8fd..5bbeb3f6a 100644
--- a/src/libslic3r/Print.hpp
+++ b/src/libslic3r/Print.hpp
@@ -416,7 +416,8 @@ public:
     const PrintObjectConfig&    default_object_config() const { return m_default_object_config; }
     const PrintRegionConfig&    default_region_config() const { return m_default_region_config; }
     const PrintObjectPtrs&      objects() const { return m_objects; }
-    const PrintObject*          get_object(int idx) const { return m_objects[idx]; }
+    PrintObject*                get_object(size_t idx) { return m_objects[idx]; }
+    const PrintObject*          get_object(size_t idx) const { return m_objects[idx]; }
     const PrintRegionPtrs&      regions() const { return m_regions; }
     const PlaceholderParser&    placeholder_parser() const { return m_placeholder_parser; }
     PlaceholderParser&          placeholder_parser() { return m_placeholder_parser; }
diff --git a/src/slic3r/GUI/MainFrame.hpp b/src/slic3r/GUI/MainFrame.hpp
index aa2041a36..ed2646b69 100644
--- a/src/slic3r/GUI/MainFrame.hpp
+++ b/src/slic3r/GUI/MainFrame.hpp
@@ -106,6 +106,8 @@ public:
     void        select_tab(size_t tab) const;
     void        select_view(const std::string& direction);
 
+    AppController* app_controller() { return m_appController; }
+
     std::vector<PresetTab>& get_preset_tabs();
 
     Plater*             m_plater { nullptr };
diff --git a/src/slic3r/GUI/Plater.cpp b/src/slic3r/GUI/Plater.cpp
index 3af670d59..f2d42806c 100644
--- a/src/slic3r/GUI/Plater.cpp
+++ b/src/slic3r/GUI/Plater.cpp
@@ -31,6 +31,7 @@
 #include "libslic3r/Format/STL.hpp"
 #include "libslic3r/Format/AMF.hpp"
 #include "libslic3r/Format/3mf.hpp"
+#include "slic3r/AppController.hpp"
 #include "GUI.hpp"
 #include "GUI_App.hpp"
 #include "GUI_ObjectList.hpp"
@@ -756,9 +757,6 @@ struct Plater::priv
 
     void remove(size_t obj_idx);
     void reset();
-    void increase(size_t num = 1);
-    void decrease(size_t num = 1);
-    void set_number_of_copies();
     void rotate();
     void mirror(const Axis &axis);
     void scale();
@@ -781,9 +779,6 @@ struct Plater::priv
     void on_layer_editing_toggled(bool enable);
 
     void on_action_add(SimpleEvent&);
-    void on_action_arrange(SimpleEvent&);
-    void on_action_more(SimpleEvent&);
-    void on_action_fewer(SimpleEvent&);
     void on_action_split(SimpleEvent&);
     void on_action_cut(SimpleEvent&);
     void on_action_settings(SimpleEvent&);
@@ -886,7 +881,7 @@ Plater::priv::priv(Plater *q, MainFrame *main_frame) :
     canvas3D->Bind(EVT_GLCANVAS_ARRANGE, [this](SimpleEvent&) { arrange(); });
     canvas3D->Bind(EVT_GLCANVAS_ROTATE_OBJECT, [this](Event<int> &evt) { /*TODO: call rotate */ });
     canvas3D->Bind(EVT_GLCANVAS_SCALE_UNIFORMLY, [this](SimpleEvent&) { scale(); });
-    canvas3D->Bind(EVT_GLCANVAS_INCREASE_OBJECTS, [this](Event<int> &evt) { evt.data == 1 ? increase() : decrease(); });
+    canvas3D->Bind(EVT_GLCANVAS_INCREASE_OBJECTS, [q](Event<int> &evt) { evt.data == 1 ? q->increase() : q->decrease(); });
     canvas3D->Bind(EVT_GLCANVAS_INSTANCE_MOVED, [this](SimpleEvent&) { update(); });
     canvas3D->Bind(EVT_GLCANVAS_WIPETOWER_MOVED, &priv::on_wipetower_moved, this);
     canvas3D->Bind(EVT_GLCANVAS_ENABLE_ACTION_BUTTONS, &priv::on_enable_action_buttons, this);
@@ -895,9 +890,9 @@ Plater::priv::priv(Plater *q, MainFrame *main_frame) :
     canvas3D->Bind(EVT_GLTOOLBAR_ADD, &priv::on_action_add, this);
     canvas3D->Bind(EVT_GLTOOLBAR_DELETE, [q](SimpleEvent&) { q->remove_selected(); } );
     canvas3D->Bind(EVT_GLTOOLBAR_DELETE_ALL, [this](SimpleEvent&) { reset(); });
-    canvas3D->Bind(EVT_GLTOOLBAR_ARRANGE, &priv::on_action_arrange, this);
-    canvas3D->Bind(EVT_GLTOOLBAR_MORE, &priv::on_action_more, this);
-    canvas3D->Bind(EVT_GLTOOLBAR_FEWER, &priv::on_action_fewer, this);
+    canvas3D->Bind(EVT_GLTOOLBAR_ARRANGE, [this](SimpleEvent&) { arrange(); });
+    canvas3D->Bind(EVT_GLTOOLBAR_MORE, [q](SimpleEvent&) { q->increase(); });
+    canvas3D->Bind(EVT_GLTOOLBAR_FEWER, [q](SimpleEvent&) { q->decrease(); });
     canvas3D->Bind(EVT_GLTOOLBAR_SPLIT, &priv::on_action_split, this);
     canvas3D->Bind(EVT_GLTOOLBAR_CUT, &priv::on_action_cut, this);
     canvas3D->Bind(EVT_GLTOOLBAR_SETTINGS, &priv::on_action_settings, this);
@@ -1388,21 +1383,6 @@ void Plater::priv::reset()
     update();
 }
 
-void Plater::priv::increase(size_t num)
-{
-    // TODO
-}
-
-void Plater::priv::decrease(size_t num)
-{
-    // TODO
-}
-
-void Plater::priv::set_number_of_copies()
-{
-    // TODO
-}
-
 void Plater::priv::rotate()
 {
     // TODO
@@ -1438,7 +1418,14 @@ void Plater::priv::scale()
 
 void Plater::priv::arrange()
 {
-    // TODO
+    // $self->stop_background_process;
+
+    main_frame->app_controller()->arrange_model();
+
+    // ignore arrange failures on purpose: user has visual feedback and we don't need to warn him
+    // when parts don't fit in print bed
+
+    update();
 }
 
 void Plater::priv::split_object()
@@ -1574,21 +1561,6 @@ void Plater::priv::on_action_add(SimpleEvent&)
     load_files(input_paths);
 }
 
-void Plater::priv::on_action_arrange(SimpleEvent&)
-{
-    // TODO
-}
-
-void Plater::priv::on_action_more(SimpleEvent&)
-{
-    // TODO
-}
-
-void Plater::priv::on_action_fewer(SimpleEvent&)
-{
-    // TODO
-}
-
 void Plater::priv::on_action_split(SimpleEvent&)
 {
     // TODO
@@ -1717,6 +1689,8 @@ Plater::~Plater()
 Sidebar& Plater::sidebar() { return *p->sidebar; }
 Model&  Plater::model()  { return p->model; }
 
+void Plater::load_files(const std::vector<fs::path> &input_files) { p->load_files(input_files); }
+
 void Plater::update(bool force_autocenter) { p->update(force_autocenter); }
 void Plater::remove(size_t obj_idx) { p->remove(obj_idx); }
 
@@ -1728,7 +1702,69 @@ void Plater::remove_selected()
     }
 }
 
-void Plater::load_files(const std::vector<fs::path> &input_files) { p->load_files(input_files); }
+void Plater::increase(size_t num)
+{
+    const auto obj_idx = p->selected_object();
+    if (! obj_idx) { return; }
+
+    auto *model_object = p->model.objects[*obj_idx];
+    auto *model_instance = model_object->instances[model_object->instances.size() - 1];
+
+    // $self->stop_background_process;
+
+    float offset = 10.0;
+    for (size_t i = 0; i < num; i++, offset += 10.0) {
+        Vec3d offset_vec = model_instance->get_offset() + Vec3d(offset, offset, 0.0);
+        auto *new_instance = model_object->add_instance(offset_vec, model_instance->get_scaling_factor(), model_instance->get_rotation());
+        p->print.get_object(*obj_idx)->add_copy(Slic3r::to_2d(offset_vec));
+    }
+
+    sidebar().obj_list()->set_object_count(*obj_idx, model_object->instances.size());
+
+    if (p->get_config("autocenter") == "1") {
+        p->arrange();
+    } else {
+        p->update();
+    }
+
+    p->selection_changed();
+
+    // $self->schedule_background_process;
+}
+
+void Plater::decrease(size_t num)
+{
+    const auto obj_idx = p->selected_object();
+    if (! obj_idx) { return; }
+
+    auto *model_object = p->model.objects[*obj_idx];
+    if (model_object->instances.size() > num) {
+        for (size_t i = 0; i < num; i++) {
+            model_object->delete_last_instance();
+            p->print.get_object(*obj_idx)->delete_last_copy();
+        }
+        sidebar().obj_list()->set_object_count(*obj_idx, model_object->instances.size());
+    } else {
+        remove(*obj_idx);
+    }
+
+    p->update();
+}
+
+void Plater::set_number_of_copies(size_t num)
+{
+    const auto obj_idx = p->selected_object();
+    if (! obj_idx) { return; }
+
+    auto *model_object = p->model.objects[*obj_idx];
+
+    auto diff = (ptrdiff_t)num - (ptrdiff_t)model_object->instances.size();
+    if (diff > 0) {
+        increase(diff);
+    } else if (diff < 0) {
+        decrease(-diff);
+    }
+}
 
 fs::path Plater::export_gcode(const fs::path &output_path)
 {
diff --git a/src/slic3r/GUI/Plater.hpp b/src/slic3r/GUI/Plater.hpp
index fd3c4e455..f8f24e2bc 100644
--- a/src/slic3r/GUI/Plater.hpp
+++ b/src/slic3r/GUI/Plater.hpp
@@ -93,11 +93,14 @@ public:
     Sidebar& sidebar();
     Model&  model();
 
+    void load_files(const std::vector<boost::filesystem::path> &input_files);
+
     void update(bool force_autocenter = false);
     void remove(size_t obj_idx);
     void remove_selected();
-
-    void load_files(const std::vector<boost::filesystem::path> &input_files);
+    void increase(size_t num = 1);
+    void decrease(size_t num = 1);
+    void set_number_of_copies(size_t num);
 
     // Note: empty path means "use the default"
     boost::filesystem::path export_gcode(const boost::filesystem::path &output_path = boost::filesystem::path());