[bthoven]

Just saw your screenshot.
In volume mapping, you need only map the main library. Remove the config mapping, you don’t need it (assuming the config folder is in your existing /Library/Ebooks folder).

If now you are running on a blank /nobody/library folder, on Calbre gui, choose Calibre Libray—>Switch library, you will see the blank folder, press up green arrow to enter the root directory.Then you will see your existing /Library folder (mapped from your /Library/Ebooks), choose it. Then you should now see all your existing ebooks catalogue.