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

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);