There have been several suggestions of this feature in multiple threads (including one from me years ago, it seems) and I'm still really hoping for this to happen one day!! I like to arrange characters based on several things including stories they're in, and sometimes one character is in multiple stories. I can't achieve this the same way with tagging either, as I can't add descriptions to tags like I can to folders, and in my experience a lot of people don't bother going through tag directories
That being said, I can manage without this feature, but I support it nevertheless! +1