Firefox's Bookmarks Toolbar is part of your overall bookmark backup (or export, if you export to HTML). Unfortunately, there is a not a convenient way to back them up separately. At least not a built-in way; there might be an add-on that can do it. If you have a different toolbar that has a bookmark feature (e.g., Yahoo toolbar), those are stored separate from Firefox's bookmarks. One way to double-check which toolbar is part of Firefox's bookmarks is to display the Bookmarks Menu or Bookmarks Sidebar, then expand Bookmarks Toolbar from there and see whether it has the bookmarks you care about.