@marty39 I dissolved the issue by disabling workspaces. All my lost tabs immediately appeared in the currently open window. That was far too many tabs for one window, so I had to move most of the tabs to other windows. But the issue is only dissolved, not solved or resolved.

I would like to be able to use the workspaces feature, but when I reenable workspaces I get the old workspace setup back, with tabs hidden in some of the workspaces. Evidently my workspace setup is corrupted. I would like to reset my workspaces (to where it was when I first enabled workspaces) but I don't know how.