My thoughts were that this should be extremely easy to do for existing users. I’d say make it a plugin but we can’t use those on layouts.
I have tried code from here…How To Create a Bottom Navigation Menu
and here…Make footer with menu stuck on bottom - #2 by Chem
and neither have worked so far.
Another option in the Menu Style as “Mobile” would allow a few seconds of clicking to create this without being forced to write code.
I’d love to see any code that you have that may help!
Edit; My suggestion is to create a separate menu for this. Not to use an existing complex one. Maybe limit it to a specific number of links and only top-level links. No sub-level menu items allowed on a Mobile Menu.