Rated 3 out of 5 stars
Those who have FF 3.*, try this out:
Doesn't help me with this particular extension, since for some unknown reason it apparently doesn't work in Linux (sigh... I deducted two stars in my rating just for that)... but will work with many, though not all, old extensions in both Windows and Linux versions.
Give it a try.
I agree that column bookmarks should be standard in Firefox. Sometimes I wonder about the developers and their decision making process ("hey man, let's make people scroll down a three or four page list to find their bookmarks! That would be funny." "Right on, man... totally hilarious... hey, pass me that joint you bogart!").