### Godot version

4.1.1

### System information

linux

### Issue description

[simplescreenrecorder-2023-08-30_15.01.51.webm](https://github.com/godotengine/godot-proposals/assets/71937306/537d92b9-4f98-4fe6-adf4-71297be0471a)

I guess this wasn't the case before since I could save a layout named "2 monitors".

### Steps to reproduce

press space

### Minimal reproduction project

none
EditorUndoRedoManager *ur = EditorUndoRedoManager::get_singleton();
	ur->create_action(TTR("Create Theme Item"));
	switch (p_data_type) {
		case Theme::DATA_TYPE_ICON:
			ur->add_do_method(*edited_theme, "set_icon", p_item_name, p_item_type, Ref<Texture2D>());
			ur->add_undo_method(*edited_theme, "clear_icon", p_item_name, p_item_type);
			break;
		case Theme::DATA_TYPE_STYLEBOX:
			ur->add_do_method(*edited_theme, "set_stylebox", p_item_name, p_item_type, Ref<StyleBox>());
			ur->add_undo_method(*edited_theme, "clear_stylebox", p_item_name, p_item_type);
			if (theme_type_editor->is_stylebox_pinned(edited_theme->get_stylebox(p_item_name, p_item_type))) {
				ur->add_undo_method(theme_type_editor, "_unpin_leading_stylebox");
			}
			break;
		case Theme::DATA_TYPE_FONT:
			ur->add_do_method(*edited_theme, "set_font", p_item_name, p_item_type, Ref<Font>());
			ur->add_undo_method(*edited_theme, "clear_font", p_item_name, p_item_type);
			break;
		case Theme::DATA_TYPE_FONT_SIZE:
			ur->add_do_method(*edited_theme, "set_font_size", p_item_name, p_item_type, -1);
			ur->add_undo_method(*edited_theme, "clear_font_size", p_item_name, p_item_type);
			break;
		case Theme::DATA_TYPE_COLOR: