There's an addon called Binder that lets you save keybindings. Including saving sets you're not currently using on any of your characters so you can bring them back later. You can have different ones for each character or one set to automatically load onto all of them.

I'm not sure about the UI though. The only addon I know of that lets you move the UI is Azurah and that has profiles for each character so you can copy settings between them, but I don't think it lets you save ones you're not currently using.

Joviex addons transfer lets you copy your ui over to other characters, if you use master merchant tho make sure to get version 4 as the tg update doesn't work with it.