Yes, but you need to use Custom CSS. Firstly you need to set that up. In Firefox type <code>about:config</code> in the Search/URL bar. When that opens type:— <code>toolkit.legacyUserProfileCustomizations.stylesheets</code> into the search box that appears — you probably won't have to finish typing before it shows in the list below. If it's value is false, double-click the word false and it will change to true. Now go to <code>about:support</code>. Look down the blue block on the left of the screen that will open until you come to Profile Directory. Click the Open Directory button next to it. This will open your Profile Directory in Windows Explorer, or whatever file browser your system uses. Make a directory/folder in that called <code>chrome</code>, all lower case. In that new folder create a text file called <code>userChrome.css</code> being careful to make sure there's a capital C in the middle. Into that file paste the code from here: https://github.com/MrOtherGuy/firefox-csshacks/blob/master/chrome/multi-row_bookmarks.css and save the file. If you're on Windows right-click it and choose Properties to make sure it really is called <code>userChrome.css</code> and not <code>userChrome.css.txt</code> and rename it if needed. Restart Firefox for it to take effect. It's a bit of a faff to set-up but having a <code>userChrome.css</code> file opens up a world of fun,