Remove the "Open Editor" button, it will open automatically.

editor/editor_node.cpp

@@ -1460,7 +1460,7 @@ void EditorNode::edit_item(Object *p_object) {
 		_set_editing_top_editors(p_object);
 		_display_top_editors(true);
 	} else {
-		_hide_top_editors();
+		hide_top_editors();
 	}
 }
 
@@ -1498,7 +1498,7 @@ void EditorNode::_save_default_environment() {
 	}
 }
 
-void EditorNode::_hide_top_editors() {
+void EditorNode::hide_top_editors() {
 
 	_display_top_editors(false);
 
@@ -1675,7 +1675,7 @@ void EditorNode::_edit_current() {
 
 		} else if (!editor_plugins_over->get_plugins_list().empty()) {
 
-			_hide_top_editors();
+			hide_top_editors();
 		}
 	}
 

editor/editor_node.h

@@ -452,7 +452,6 @@ private:
 
 	void _instance_request(const Vector<String> &p_files);
 
-	void _hide_top_editors();
 	void _display_top_editors(bool p_display);
 	void _set_top_editors(Vector<EditorPlugin *> p_editor_plugins_over);
 	void _set_editing_top_editors(Object *p_current_object);
@@ -677,6 +676,7 @@ public:
 	void edit_item(Object *p_object);
 	void edit_item_resource(RES p_resource);
 	bool item_has_editor(Object *p_object);
+	void hide_top_editors();
 
 	void open_request(const String &p_path);
 

editor/editor_properties.cpp

@@ -2443,6 +2443,38 @@ void EditorPropertyResource::_open_editor_pressed() {
 	}
 }
 
+void EditorPropertyResource::_fold_other_editors(Object *p_self) {
+
+	if (this == p_self) {
+		return;
+	}
+
+	RES res = get_edited_object()->get(get_edited_property());
+
+	if (!res.is_valid())
+		return;
+	bool use_editor = false;
+	for (int i = 0; i < EditorNode::get_singleton()->get_editor_data().get_editor_plugin_count(); i++) {
+		EditorPlugin *ep = EditorNode::get_singleton()->get_editor_data().get_editor_plugin(i);
+		if (ep->handles(res.ptr())) {
+			use_editor = true;
+		}
+	}
+
+	if (!use_editor)
+		return;
+	bool unfolded = get_edited_object()->editor_is_section_unfolded(get_edited_property());
+
+	if (unfolded) {
+		//refold
+		assign->set_pressed(false);
+		get_edited_object()->editor_set_section_unfold(get_edited_property(), false);
+		update_property();
+	}
+
+	opened_editor = false;
+}
+
 void EditorPropertyResource::update_property() {
 
 	RES res = get_edited_object()->get(get_edited_property());
@@ -2487,12 +2519,20 @@ void EditorPropertyResource::update_property() {
 				}
 
 				if (use_editor) {
+					//open editor directly and hide other open of these
+					_open_editor_pressed();
+					if (is_inside_tree()) {
+						get_tree()->call_deferred("call_group", "_editor_resource_properties", "_fold_other_editors", this);
+					}
+					opened_editor = true;
+					/*
 					Button *open_in_editor = memnew(Button);
 					open_in_editor->set_text(TTR("Open Editor"));
 					open_in_editor->set_icon(get_icon("Edit", "EditorIcons"));
 					sub_inspector_vbox->add_child(open_in_editor);
 					open_in_editor->connect("pressed", this, "_open_editor_pressed");
 					open_in_editor->set_h_size_flags(SIZE_SHRINK_CENTER);
+					*/
 				}
 			}
 
@@ -2506,6 +2546,10 @@ void EditorPropertyResource::update_property() {
 				memdelete(sub_inspector_vbox);
 				sub_inspector = NULL;
 				sub_inspector_vbox = NULL;
+				if (opened_editor) {
+					EditorNode::get_singleton()->hide_top_editors();
+					opened_editor = false;
+				}
 			}
 		}
 #endif
@@ -2726,10 +2770,12 @@ void EditorPropertyResource::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("_button_draw"), &EditorPropertyResource::_button_draw);
 	ClassDB::bind_method(D_METHOD("_open_editor_pressed"), &EditorPropertyResource::_open_editor_pressed);
 	ClassDB::bind_method(D_METHOD("_button_input"), &EditorPropertyResource::_button_input);
+	ClassDB::bind_method(D_METHOD("_fold_other_editors"), &EditorPropertyResource::_fold_other_editors);
 }
 
 EditorPropertyResource::EditorPropertyResource() {
 
+	opened_editor = true;
 	sub_inspector = NULL;
 	sub_inspector_vbox = NULL;
 	use_sub_inspector = bool(EDITOR_GET("interface/inspector/open_resources_in_current_inspector"));
@@ -2766,6 +2812,8 @@ EditorPropertyResource::EditorPropertyResource() {
 	file = NULL;
 	scene_tree = NULL;
 	dropping = false;
+
+	add_to_group("_editor_resource_properties");
 }
 
 ////////////// DEFAULT PLUGIN //////////////////////

editor/editor_properties.h

@@ -581,6 +581,9 @@ class EditorPropertyResource : public EditorProperty {
 
 	void _button_input(const Ref<InputEvent> &p_event);
 	void _open_editor_pressed();
+	void _fold_other_editors(Object *p_self);
+
+	bool opened_editor;
 
 protected:
 	static void _bind_methods();

editor/editor_resource_preview.h

@@ -36,24 +36,6 @@
 #include "scene/main/node.h"
 #include "scene/resources/texture.h"
 
-/* make previews for:
-*packdscene
-*wav
-*image
-*mesh
--font
-*script
-*material
--shader
--shader graph?
--navigation mesh
--collision?
--occluder polygon
--navigation polygon
--tileset
--curve and curve2D
-*/
-
 class EditorResourcePreviewGenerator : public Reference {
 
 	GDCLASS(EditorResourcePreviewGenerator, Reference);