I found that it's possible to leave the second field blank, so I'm grouping them in my original backup folder:
At the moment I'm thinking this will create more backups than I need, as I do quite frequent Calibre restarts. Perhaps a GUI button to run it on demand would be the best solution for my case but I'm aware of the risks of creating a config backup while Calibre is running.
(yet I've never had issues after restoring backups made with the script I run, which most times I do with Calibre running
)