If you expand a bookmark with sub-bookmarks when in Add Bookmark, then they stay expanded. You can easily end up with a number of expanded bookmarks and, before you know it, you have to scroll down for ages if you want to reach somewhere at the bottom of the bookmark list. Manage Bookmarks behaves similarly in that expanded bookmarks stay expanded.
Now, yes, I know that if I were neat and tidy and collapsed bookmarks when I finished with them I wouldn't have a problem, but I'm not (and never likely to be
). So, the question is, is it possible to collapse all expanded bookmarks with one keystroke.
I did ask in the Mozilla forums, without any luck, which suggests that the answer may be, no. On the other hand, you get so many questions on those forums that, unless you get an answer almost straight away, your question disappears into the wild blue yonder very quickly.