Evren Carven, at MacRumors, posted the solution. 'Tis a wee bit awkward, but otherwise works:

In Photos-
1. Go to menu: View - Metadata, and enable "Titles".

2. Right click a photo and choose 'Get Info' to add a title for the photo with the "Add a Title" option. You can also add key words and a description.

Indeed I never would have divined the solution/fix... but I should have.

Harv
27" i7 iMac (10.13.6), iPhone Xs Max (12.1)

Those who can make you believe absurdities can make you commit atrocities. ~Voltaire