This excellent addon's name, summary, and screenshots don't do a good job of conveying what this addon does, how you'd use it, and why it's useful. This addon is useful if you have a lot of bookmark folders. It saves you time by helping you quickly find the folder you want to add the bookmark to.

You type the folder's name into a search box and it displays all relevant bookmark folders. This lets you find your desired folder MUCH faster than if you were to use Firefox's default add-bookmark editor (which uses drop-down menus and may requires a LOT of clicks to find the folder you want).

I think this addon would have a lot more downloads if its functionality, usage, and usefulness were more clearly explained. I had to install and try this addon in order to fully understand what it does and to realize that it's something I've always wanted.