Have more than a few bookmarks you want to keep handy on the bookmarks toolbar in Firefox but don’t have the room? Multirow Bookmarks Toolbar, an extension for Firefox, will help you solve that issue by letting you add as many bookmark toolbars as you need.
Once installed, the options here are simple. You can enable or disable the multiple bookmark rows, and you can also set the max number rows to display. If it doesn’t exactly match up with your current theme or you want to tweak it some, check out this post from the mozillazine.org forums.
If you need more bookmark room in the browser, this add-on will do the trick. You can pick it up on the Firefox Add-ons site.