Description:
	I would like a new feature where “View -> User Interface...” lets me create and save my own custom UI variants. There are a few reasons for this:
	Even though each User Interface autosaves its most recent toolbar arrangement, I don’t feel like I’m “saving and restoring *my* UI”. I still instinctively think of the options listed as pre-made setups from the LibreOffice design team.
	In Draw, I accidentally created an excellent vertical UI while set to the “sidebar” user interface. Now I have to remember that Writer and Calc’s “Sidebar” is good for horizontal displays, but Draw’s “Sidebar” is good for my vertical monitor. If I could save my Draw layout to a custom named UI variant, it would simplify getting to a layout that I know “just works” for me.
	It took a lot of trial and error to figure out LibreOffice’s UI, and these experiments essentially destroyed the Standard UI in Writer. I am forced to use Notebookbar or Sidebar, or spend extra time piecing Writer’s Standard UI back together. For this reason, I believe the default layouts (Like Tabbed and GroupedBar) should fully reset the UI to default, rather than remember a user’s modifications.
	In order to make a full reset like this possible, LibreOffice’s default toolbars should not be editable. Attempting to edit a default Toolbar should prompt the user to “save as” a new toolbar with a new name. It would be like using a Template file.

Steps to Reproduce:
1. Activate the Menu Bar if it is not visible.
2. Choose View
3. From the View dropdown, choose User Interface...
4. Select a UI variant from the list provided.

Actual Results:
In the Select Your Preferred User Interface dialog box, there are 7 UI variants to choose from. The current User Interface is automatically customized whenever a change is made by the user.

Expected Results:
The 7 UI variants listed should act as defaults.
When a user decides to switch to a new UI, a prompt should appear asking if they want to save their current UI with options Save, Save as, Don't Save, and Cancel.
If the current UI was a premade UI, the Save button will be grayed out, forcing the user to save their layout as a new variant. Otherwise, clicking Save will overwrite any changes they made to the custom UI they were using.
If the user selects Save As, a text box will appear prompting for a layout name and an optional description.
Choosing Don't Save will discard any UI changes made since the last save.
Choosing Cancel will keep the user on their current UI layout instead of switching to a new layout.


Reproducible: Always


User Profile Reset: No



Additional Info:
There should be a way to save your current layout or duplicate a custom layout without switching to a new layout.