After going through a round of loops of circles of the layout problem bug:
Can not Launch Unity Due to "Failed to load window layout" page-5
The editor has become more responsive. Somewhat.
And I’ve found the font that was causing the problem. It’s the original font… from the start of the project, that’s never been used. No idea why it’s complaining, all of a sudden. But now getting dozens of other build preventing problems, one after another.
Probably resolve all of them in a few days.