Just close that tab.
You don't really need to .. it has it's own backup system in .json anyhow .. and there are a load of them in the Profile folder.
http://kb.mozillazine...g_bookmarks_-_Firefox
Just delete what you need to on the toolbar .. bookmarks will still be there as they should have been copied from the bookmarks sidebar. You can L-click on, and drag into the sidebar if you need to.
As I said before, Help/restart without add-ons .. and select reset toolbars.
Even though I close that tag which sits side by side my homepage tag, it makes no difference because it appears everytime I start firefox.
Since I installed the latest version of firefox, I do not have a sidebar with all my overfill bookmarks in it, they are now all along the bookmark toolbar space.in smaller icons.
What with this tool bar not loading on start-up problem and this addition problem I am getting so fed-up that I am considering going back to the very much earlier version of firefox.
The Bookmark Toolbar .. is not the bookmark list.
The toolbar and the Bookmark (sidebar) are different things.
Treat the toolbar as a holder for 'quick-start' one-click bookmarks.
You should have a default live bookmark in there with a drop-down 'Latest Headlines'