I'm not sure if I understand your comment. Firefox does allow you to organize bookmarks by tag, and it even lets you use the tag collection as a bookmark folder (meaning that you can add the tag to the bookmark bar and it behaves like a normal bookmark folder.) You can even add different links to different bookmark folders and give them the same tag, so that they appear under the original bookmark folder and under the same tag category, or tag folder if you drag the tag to the bookmark bar. If you decide to remove the tag folder from the bookmark bar, the tag will still exist.