Thanks. I followed the 'start in safe mode' instructions as best I could.
After I selected the volume and held down the SHIFT key, I got the option to CONTINUE, but not an option to CONTINUE IN SAFE MODE.
When the computer turned off (after holding down the power button) the screen was black, and I lost the ability to use my mouse, so I navigated with the arrows.
Long story short, the computer restarted, but I could see nothing about SAFE BOOT in the menu bar.
I presume that menu bar is at the top?
Any pointers for retrying starting in safe mode? I'm sure it's somehow my fault, but all I could see was "continue" and not "continue in safe mode."
At worst, this is a feature I could live without. I use "Stage Manager" off and on, and I thought that might cause the glitch, but the problem persists with I'm using Stage Manager or not.