So, in the subject of "what has mysteriously changed today in S22" I suddenly find I cannot right-click the timeline "ruler" to get the menu that allows me to choose specific amount of timeline display - or show entire project.

I right-click and nothing happens. All other right-click menus are working and I can still change the timeline size; by dragging the positioning slider at the very bottom or by using numpad minus and plus. 

I've reloaded, I've rebooted. I've tried different projects and I've started a new project. Still no right-click to change timeline size or select "entire movie". It worked when I went to bed last night... maybe it doesn't like Wednesdays.

WOW! How bizarre. You are spot on (again). No, it was not check marked. But how did it become uncheck marked?? I've not been in that menu since I first setup S22 about 2 months ago. Weird.

Thank you.

I can not answer how it got unchecked... things happen.

But glad you have it working now!