How to back up folder/files within the MacOS Library folder

I tried the option –snapshot-policy = required but that gives this error:

An error occurred trying to start process '/Applications/Duplicati.app/Contents/MacOS/lvm-scripts/find-volume.sh' with working directory '/'

Perhaps I need to borrow your scripts @madfordmac

As new Duplicati user on MacOS the experience feels a bit rough so far. Opened a new thread with some examples here.