So it turns out that I CAN do this with the photos OUTSIDE of the Apple Photos library using Photo Supreme, Graphic Converter (already tested both) and “probably” Photo Mechanic. So THAT would mean exporting out all the photos from the library, doing the process, then re-importing into AP -OR- simply delete the library, do the thing externally, then re-export the (mainly raw) files out (again) to compressed HEIC or JpegXL and then re-import into a blank library…either way a huge PITA.
I’d much prefer to do it inside the library, but it may not be possible. It appears that Nitro also follows the same requirement in a Photo Library window, where it clearly does NOT in a folder view.
So definitely hoping for some enlightenment.
thanks
gary