What you’re looking for is Mikey’s toolbox
It’s a bit old, but it is the only tool I know of that does what you are looking for.
I don’t know if it still works.
Alternatively you could try the zip file method, every time you want to change saves add all the game.db files to a zip named for the character, then unzip the save with the character you want to switch.
I use this method and I used to test mods, and I still have my original save game from 2017.
7zip is a free archiver if you need one.
This method is very tedious but offers really good results in that you end up with lots back up saves.