Import project

src/slic3r/GUI/GUI_App.cpp

@@ -8905,7 +8905,11 @@ void GUI_App::load_current_presets(bool active_preset_combox/*= false*/, bool ch
     if (printer_technology == ptFFF && !edited_printer_preset.config.opt_bool("single_extruder_multi_material")) {
         auto* nozzle_diameter = edited_printer_preset.config.option<ConfigOptionFloats>("nozzle_diameter");
         if (nozzle_diameter) {
-            preset_bundle->set_num_filaments(nozzle_diameter->values.size());
+            // Mixed-color slots are virtual filaments kept at the tail of the list, so they have no
+            // nozzle of their own. Sizing to the nozzle count alone truncates them away — and this
+            // runs right after a project is loaded, so it would silently drop the project's mixes
+            // and then let update_extruder_count() strip every painted facet above the new count.
+            preset_bundle->set_num_filaments(nozzle_diameter->values.size() + preset_bundle->num_mixed_filaments());
         }
     }
 	this->plater()->set_printer_technology(printer_technology);

src/slic3r/GUI/Tab.cpp

@@ -2182,8 +2182,11 @@ void Tab::on_value_change(const std::string& opt_key, const boost::any& value)
             std::string new_color = new_col.GetAsString(wxC2S_HTML_SYNTAX).ToStdString();
             new_colors.push_back(new_color);
         }
-        wxGetApp().preset_bundle->set_num_filaments(num_extruder, new_colors);
-        wxGetApp().plater()->on_filament_count_change(num_extruder);
+        // Mixed-color slots are virtual filaments at the tail of the list with no nozzle of their
+        // own, so they are carried on top of the new extruder count instead of being truncated.
+        const size_t total_filaments = num_extruder + wxGetApp().preset_bundle->num_mixed_filaments();
+        wxGetApp().preset_bundle->set_num_filaments(total_filaments, new_colors);
+        wxGetApp().plater()->on_filament_count_change(total_filaments);
         wxGetApp().get_tab(Preset::TYPE_PRINT)->update();
         wxGetApp().preset_bundle->export_selections(*wxGetApp().app_config);
     }