### 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("Set Color Item in Theme"), UndoRedo::MERGE_ENDS);
	ur->add_do_method(*edited_theme, "set_color", p_item_name, edited_type, p_value);
	ur->add_undo_method(*edited_theme, "set_color", p_item_name, edited_type, edited_theme->get_color(p_item_name, edited_type));
	ur->commit_action();
}
void ThemeTypeEditor::_constant_item_changed(float p_value, String p_item_name) {
	EditorUndoRedoManager *ur = EditorUndoRedoManager::get_singleton();
	ur->create_action(TTR("Set Constant Item in Theme"));
	ur->add_do_method(*edited_theme, "set_constant", p_item_name, edited_type, p_value);
	ur->add_undo_method(*edited_theme, "set_constant", p_item_name, edited_type, edited_theme->get_constant(p_item_name, edited_type));
	ur->commit_action();
}
void ThemeTypeEditor::_font_size_item_changed(float p_value, String p_item_name) {
	EditorUndoRedoManager *ur = EditorUndoRedoManager::get_singleton();
	ur->create_action(TTR("Set Font Size Item in Theme"));
	ur->add_do_method(*edited_theme, "set_font_size", p_item_name, edited_type, p_value);
	ur->add_undo_method(*edited_theme, "set_font_size", p_item_name, edited_type, edited_theme->get_font_size(p_item_name, edited_type));
	ur->commit_action();
}
void ThemeTypeEditor::_edit_resource_item(Ref<Resource> p_resource, bool p_edit) {