Simple mode: Emboss related improvements:

* Deleted "Add text part/negative volume" items from context menu
* Disable menu item "Split to parts" for object's context menu
* "T"-key doesn't cause an adding of the text-part
* Load 3mf by DnD: Add info dialog for a case of "Load geometry"
  + Change No button to Cancel

src/slic3r/GUI/GUI_ObjectList.cpp

@@ -2480,6 +2480,9 @@ bool ObjectList::is_splittable(bool to_objects)
         return false;
     }
 
+    if (wxGetApp().get_mode() == comSimple)
+        return false; // suppress to split to parts for simple mode
+
     ModelVolume* volume;
     if (!get_volume_by_item(item, volume) || !volume)
         return false;