Somehow I have a third workspace for bases shared with me. How do I remove it?
Remove yourself from any bases shared with you. It looks like you have one base there that is owned by someone else, but they have invited you to collaborate on. If you go into the sharing menu in that base and remove yourself as a collaborator, the Shared With Me section should disappear. No bases shared with you means no shared with me section!
Thank you very much indeed!