### 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
edit_add_type_value = memnew(LineEdit);
	edit_add_type_value->set_h_size_flags(Control::SIZE_EXPAND_FILL);
	edit_add_type_value->connect("text_submitted", callable_mp(this, &ThemeItemEditorDialog::_add_theme_type));
	edit_add_type_hb->add_child(edit_add_type_value);
	edit_add_type_button = memnew(Button);
	edit_add_type_hb->add_child(edit_add_type_button);
	edit_add_type_button->connect("pressed", callable_mp(this, &ThemeItemEditorDialog::_add_theme_type).bind(""));
	VBoxContainer *edit_items_vb = memnew(VBoxContainer);
	edit_items_vb->set_h_size_flags(Control::SIZE_EXPAND_FILL);
	edit_dialog_hs->add_child(edit_items_vb);
	HBoxContainer *edit_items_toolbar = memnew(HBoxContainer);
	edit_items_vb->add_child(edit_items_toolbar);
	Label *edit_items_toolbar_add_label = memnew(Label);
	edit_items_toolbar_add_label->set_text(TTR("Add Item:"));
	edit_items_toolbar->add_child(edit_items_toolbar_add_label);
	edit_items_add_color = memnew(Button);
	edit_items_add_color->set_tooltip_text(TTR("Add Color Item"));
	edit_items_add_color->set_flat(true);
	edit_items_add_color->set_disabled(true);
	edit_items_toolbar->add_child(edit_items_add_color);
	edit_items_add_color->connect("pressed", callable_mp(this, &ThemeItemEditorDialog::_open_add_theme_item_dialog).bind(Theme::DATA_TYPE_COLOR));
	edit_items_add_constant = memnew(Button);
	edit_items_add_constant->set_tooltip_text(TTR("Add Constant Item"));
	edit_items_add_constant->set_flat(true);
	edit_items_add_constant->set_disabled(true);
	edit_items_toolbar->add_child(edit_items_add_constant);
	edit_items_add_constant->connect("pressed", callable_mp(this, &ThemeItemEditorDialog::_open_add_theme_item_dialog).bind(Theme::DATA_TYPE_CONSTANT));
	edit_items_add_font = memnew(Button);
	edit_items_add_font->set_tooltip_text(TTR("Add Font Item"));
	edit_items_add_font->set_flat(true);