Have some data stored in notebooks and is going to be a pain if I can’t get that back!! One of the top bars contains New note, New to-do, and New notebook. New to-do also has a box with a check-mark that never goes away. Just to see what it does I clicked on New to-do. The box for that area changed from white to blue and at that point Joplin hung.
At this point nothing works. Closing Joplin and restarting does not change anything - still hung. The screen looks exactly as it did when the problem started.