### 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
List<StringName> names;
	String default_type = edited_type;
	if (edited_theme->get_type_variation_base(edited_type) != StringName()) {
		default_type = edited_theme->get_type_variation_base(edited_type);
	}
	Ref<Theme> old_snapshot = edited_theme->duplicate();
	Ref<Theme> new_snapshot = edited_theme->duplicate();
	updating = true;
	{
		names.clear();
		ThemeDB::get_singleton()->get_default_theme()->get_icon_list(default_type, &names);
		for (const StringName &E : names) {
			if (!new_snapshot->has_icon(E, edited_type)) {
				new_snapshot->set_icon(E, edited_type, ThemeDB::get_singleton()->get_default_theme()->get_icon(E, edited_type));
			}
		}
	}
	{
		names.clear();
		ThemeDB::get_singleton()->get_default_theme()->get_stylebox_list(default_type, &names);
		for (const StringName &E : names) {
			if (!new_snapshot->has_stylebox(E, edited_type)) {
				new_snapshot->set_stylebox(E, edited_type, ThemeDB::get_singleton()->get_default_theme()->get_stylebox(E, edited_type));
			}