Ability to tag a thread would be extremely helpful

E.g. today I wanted to look back on the book recommendation threads in the Lounge. But for using the "search" tool, I need to know specific keywords. E.g. if I search for "books" I get a 100 unrelated threads. (people refer to books in threads about other things as well)

If, when I create a thread, I can tag it with "book recommendations" or "money saving tips" it would be so much easier to pull up relevant threads.