OK folks, I did as I said. I just completed the re download of ST10. The BLOCK/EDIT/CUSTOMIZE looks the same and does not have the Block - Editenvironment as a selection. But now I have my customizations back.
So Sean's suspicion re blame it on MS may well be the answer. But I guess until somebody fixes it, I'm going to live without using the BLOCK/EDIT command.
Sean, my poor use of the language. Yes, I can BLOCK/EDIT in the conventional way. But it means using a RADIAL MENU that I'm not familar with. However, after the redownload, I did get my custom QUICK ACCESS TOOLBAR that I had set up for BLOCK/EDIT. I don't think that I noticed it before. So, although the radial is strange, I may still use the BLOCK/EDIT when necessary. This is really no big deal because, for me, I had hardly used this command anyway and only started using it a bit more in ST9.
Apparently, I'm the only one who has been affected by this problem, or the first to notice it.