I always keep so many tabs open in my Firefox browser that they are inconvenient to search because they are all on one line and you have to scroll through them horizontally. Seeing how easy it is to organize the top bookmarks bar instead, I realized that it would be great if you could organize the tabs like bookmarks, with dropdown menus and submenus and separators. The next step might be to find a way to unify bookmarks and tabs, harmonizing the static features of the former and the dynamic features of the latter.