So if I were to back up my Rejuvenation data if I wanted to start a new file, I'd just take the file in Saved Games and copy/move it somewhere else, right?
Copying it would let you create a backup I suppose, but not give capacity to start a new game. Moving the current save file elsewhere would allow you to start a new game, yes. Just be sure to keep track of which save is which (you can rename saves).