Found an answer in another forum, and as I suspected, it's something Microsoft decided to take from us. God forbid we'f have any sort of control over our systems' appearance and function. Here's the excerpt for anyone else confused by this idiotic change.
That's another feature that has been dropped with the latest Explorer in Windows 11. You can post a complaint about that via Feedback Hub. I'm sure others have, but more the better.
The workaround is to change to Details view, where you still get "More" by clicking in the column heading area, add the additional property, and then change back to whatever view you were in. The additional property will now be in the Sort by list.