Thanks Gracille — If I delete my account and start a new one, what's the most straightforward way to migrate all of my library from the old account to the new?
All data are stored locally. Just change the username in the Sync pane of the Preferences. The next sync will transfer all your data to your new account on the server. (also you'd have to join again groups - and to transfer ownerships of your groups if any)
(also you'd have to join again groups - and to transfer ownerships of your groups if any)