I Really Did Not Want to Re-Do My Visual Filters - Thank you Faithlife!
Actually I suspect this is just a continuing saga of what Bradley euphemistically calls the L10 M1 "performance regression". [edited]
Earlier, after I dutifully deleted my search-based visual filters to at least be able to run L10 decently, I thought I'd put them back (with the new search syntax ... which looks suspiciously like the old syntax).
I went to Documents, Add > Visual Filter, and Open, and waited and waited. Something happened but nothing I could see. After a bit of trial and error, it appears to open a panel, and promptly shuts it. Then deletes my untitled VF in the list ... plus all the other docs. Not really ... clicking the filter button brings back the others, just not the 'new' VF. Whew.
This also looks like the failing Timeline (used to be the failing Advanced Timeline ... it got 'regressed').
Sorry for all the humor. I'd not do well in Faithlife Marketing