About be complicated or not, I can't give an opinion, but I'm totally convinced that would be a great feature. The beauty of Nostr is about experiment things, not clone what already exists. I vote to do things in different ways, haha.

I think the user would simply click on the group of notes, and all of them would be considered read. When the page was refreshed, the note groups would be renewed. If the user hadn't read them, they could mark them as "unread" in the note group, so it wouldn't be renewed. They could also mark specific notes as "unread" if they hadn't read them but would like to read them later, so they would remain in the note group after the page refresh.