Now menu items can be added to the convert menu in the editor.

editor/editor_node.cpp

@@ -2892,6 +2892,27 @@ void EditorNode::_tool_menu_option(int p_idx) {
 	}
 }
 
+void EditorNode::_convert_button_menu_option(int p_idx) {
+	switch (convert_menu->get_item_id(p_idx)) {
+		case FILE_CONVERT_CUSTOM: {
+			if (convert_menu->get_item_submenu(p_idx) == "") {
+				Array params = convert_menu->get_item_metadata(p_idx);
+
+				Object *handler = ObjectDB::get_instance(params[0]);
+				String callback = params[1];
+				Variant *ud = &params[2];
+				Variant::CallError ce;
+
+				handler->call(callback, (const Variant **)&ud, 1, ce);
+				if (ce.error != Variant::CallError::CALL_OK) {
+					String err = Variant::get_call_error_text(handler, callback, (const Variant **)&ud, 1, ce);
+					ERR_PRINT("Error calling function from convert menu: " + err);
+				}
+			} // else it's a submenu so don't do anything.
+		} break;
+	}
+}
+
 int EditorNode::_next_unsaved_scene(bool p_valid_filename, int p_start) {
 	for (int i = p_start; i < editor_data.get_edited_scene_count(); i++) {
 		if (!editor_data.get_edited_scene_root(i)) {
@@ -5307,6 +5328,46 @@ void EditorNode::remove_tool_menu_item(const String &p_name) {
 	}
 }
 
+void EditorNode::add_convert_menu_item(const String &p_name, Object *p_handler, const String &p_callback, const Variant &p_ud) {
+	ERR_FAIL_NULL(p_handler);
+	int idx = convert_menu->get_item_count();
+	convert_menu->add_item(p_name, FILE_CONVERT_CUSTOM);
+
+	Array parameters;
+	parameters.push_back(p_handler->get_instance_id());
+	parameters.push_back(p_callback);
+	parameters.push_back(p_ud);
+
+	convert_menu->set_item_metadata(idx, parameters);
+}
+
+void EditorNode::add_convert_submenu_item(const String &p_name, PopupMenu *p_submenu) {
+	ERR_FAIL_NULL(p_submenu);
+	ERR_FAIL_COND(p_submenu->get_parent() != nullptr);
+
+	convert_menu->add_child(p_submenu);
+	convert_menu->add_submenu_item(p_name, p_submenu->get_name(), FILE_CONVERT_CUSTOM);
+}
+
+void EditorNode::remove_convert_menu_item(const String &p_name) {
+	for (int i = 0; i < convert_menu->get_item_count(); i++) {
+		if (convert_menu->get_item_id(i) != FILE_CONVERT_CUSTOM) {
+			continue;
+		}
+
+		if (convert_menu->get_item_text(i) == p_name) {
+			if (convert_menu->get_item_submenu(i) != "") {
+				Node *n = convert_menu->get_node(convert_menu->get_item_submenu(i));
+				convert_menu->remove_child(n);
+				memdelete(n);
+			}
+			convert_menu->remove_item(i);
+			convert_menu->set_as_minsize();
+			return;
+		}
+	}
+}
+
 void EditorNode::_global_menu_action(const Variant &p_id, const Variant &p_meta) {
 	int id = (int)p_id;
 	if (id == GLOBAL_NEW_WINDOW) {
@@ -5564,6 +5625,7 @@ void EditorNode::_project_settings_changed() {
 void EditorNode::_bind_methods() {
 	ClassDB::bind_method("_menu_option", &EditorNode::_menu_option);
 	ClassDB::bind_method("_tool_menu_option", &EditorNode::_tool_menu_option);
+	ClassDB::bind_method("_convert_button_menu_option", &EditorNode::_convert_button_menu_option);
 	ClassDB::bind_method("_menu_confirm_current", &EditorNode::_menu_confirm_current);
 	ClassDB::bind_method("_dialog_action", &EditorNode::_dialog_action);
 	ClassDB::bind_method("_editor_select", &EditorNode::_editor_select);
@@ -6263,11 +6325,11 @@ EditorNode::EditorNode() {
 	p->add_shortcut(ED_SHORTCUT("editor/quick_open_script", TTR("Quick Open Script..."), KEY_MASK_ALT + KEY_MASK_CMD + KEY_O), FILE_QUICK_OPEN_SCRIPT);
 
 	p->add_separator();
-	PopupMenu *pm_export = memnew(PopupMenu);
+	convert_menu = memnew(PopupMenu);
-	pm_export->set_name("Export");
+	convert_menu->set_name("Export");
-	p->add_child(pm_export);
+	p->add_child(convert_menu);
 	p->add_submenu_item(TTR("Convert To..."), "Export");
-	pm_export->connect("id_pressed", this, "_menu_option");
+	convert_menu->connect("index_pressed", this, "_convert_button_menu_option");
 
 	p->add_separator();
 	p->add_shortcut(ED_SHORTCUT("editor/undo", TTR("Undo"), KEY_MASK_CMD + KEY_Z), EDIT_UNDO, true);

editor/editor_node.h

@@ -342,6 +342,10 @@ public:
 	void add_tool_submenu_item(const String &p_name, PopupMenu *p_submenu);
 	void remove_tool_menu_item(const String &p_name);
 
+	void add_convert_menu_item(const String &p_name, Object *p_handler, const String &p_callback, const Variant &p_ud = Variant());
+	void add_convert_submenu_item(const String &p_name, PopupMenu *p_submenu);
+	void remove_convert_menu_item(const String &p_name);
+
 	void save_all_scenes();
 	void save_scene_list(Vector<String> p_scene_filenames);
 	void restart_editor();
@@ -419,6 +423,7 @@ private:
 		FILE_CLOSE_ALL_AND_RELOAD_CURRENT_PROJECT,
 		FILE_QUIT,
 		FILE_EXTERNAL_OPEN_SCENE,
+		FILE_CONVERT_CUSTOM,
 		EDIT_UNDO,
 		EDIT_REDO,
 		EDIT_RELOAD_SAVED_SCENE,
@@ -541,6 +546,7 @@ private:
 	HBoxContainer *menu_hb;
 	Control *viewport;
 	MenuButton *file_menu;
+	PopupMenu *convert_menu;
 	MenuButton *project_menu;
 	MenuButton *debug_menu;
 	MenuButton *settings_menu;
@@ -752,6 +758,7 @@ private:
 	void _save_screenshot(NodePath p_path);
 
 	void _tool_menu_option(int p_idx);
+	void _convert_button_menu_option(int p_idx);
 	void _update_debug_options();
 	void _update_file_menu_opened();
 	void _update_file_menu_closed();

editor/editor_plugin.cpp

@@ -555,6 +555,21 @@ void EditorPlugin::remove_tool_menu_item(const String &p_name) {
 	EditorNode::get_singleton()->remove_tool_menu_item(p_name);
 }
 
+void EditorPlugin::add_convert_menu_item(const String &p_name, Object *p_handler, const String &p_callback, const Variant &p_ud) {
+	EditorNode::get_singleton()->add_convert_menu_item(p_name, p_handler, p_callback, p_ud);
+}
+
+void EditorPlugin::add_convert_submenu_item(const String &p_name, Object *p_submenu) {
+	ERR_FAIL_NULL(p_submenu);
+	PopupMenu *submenu = Object::cast_to<PopupMenu>(p_submenu);
+	ERR_FAIL_NULL(submenu);
+	EditorNode::get_singleton()->add_convert_submenu_item(p_name, submenu);
+}
+
+void EditorPlugin::remove_convert_menu_item(const String &p_name) {
+	EditorNode::get_singleton()->remove_convert_menu_item(p_name);
+}
+
 void EditorPlugin::set_input_event_forwarding_always_enabled() {
 	input_event_forwarding_always_enabled = true;
 	EditorPluginList *always_input_forwarding_list = EditorNode::get_singleton()->get_editor_plugins_force_input_forwarding();
@@ -863,12 +878,19 @@ void EditorPlugin::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("add_control_to_container", "container", "control"), &EditorPlugin::add_control_to_container);
 	ClassDB::bind_method(D_METHOD("add_control_to_bottom_panel", "control", "title"), &EditorPlugin::add_control_to_bottom_panel);
 	ClassDB::bind_method(D_METHOD("add_control_to_dock", "slot", "control"), &EditorPlugin::add_control_to_dock);
+	
 	ClassDB::bind_method(D_METHOD("remove_control_from_docks", "control"), &EditorPlugin::remove_control_from_docks);
 	ClassDB::bind_method(D_METHOD("remove_control_from_bottom_panel", "control"), &EditorPlugin::remove_control_from_bottom_panel);
 	ClassDB::bind_method(D_METHOD("remove_control_from_container", "container", "control"), &EditorPlugin::remove_control_from_container);
+	
 	ClassDB::bind_method(D_METHOD("add_tool_menu_item", "name", "handler", "callback", "ud"), &EditorPlugin::add_tool_menu_item, DEFVAL(Variant()));
 	ClassDB::bind_method(D_METHOD("add_tool_submenu_item", "name", "submenu"), &EditorPlugin::add_tool_submenu_item);
 	ClassDB::bind_method(D_METHOD("remove_tool_menu_item", "name"), &EditorPlugin::remove_tool_menu_item);
+
+	ClassDB::bind_method(D_METHOD("add_convert_menu_item", "name", "handler", "callback", "ud"), &EditorPlugin::add_convert_menu_item, DEFVAL(Variant()));
+	ClassDB::bind_method(D_METHOD("add_convert_submenu_item", "name", "submenu"), &EditorPlugin::add_convert_submenu_item);
+	ClassDB::bind_method(D_METHOD("remove_convert_menu_item", "name"), &EditorPlugin::remove_convert_menu_item);
+	
 	ClassDB::bind_method(D_METHOD("add_custom_type", "type", "base", "script", "icon"), &EditorPlugin::add_custom_type);
 	ClassDB::bind_method(D_METHOD("remove_custom_type", "type"), &EditorPlugin::remove_custom_type);
 

editor/editor_plugin.h

@@ -211,6 +211,10 @@ public:
 	void add_tool_submenu_item(const String &p_name, Object *p_submenu);
 	void remove_tool_menu_item(const String &p_name);
 
+	void add_convert_menu_item(const String &p_name, Object *p_handler, const String &p_callback, const Variant &p_ud = Variant());
+	void add_convert_submenu_item(const String &p_name, Object *p_submenu);
+	void remove_convert_menu_item(const String &p_name);
+
 	void set_input_event_forwarding_always_enabled();
 	bool is_input_event_forwarding_always_enabled() { return input_event_forwarding_always_enabled; }