When you use vertical tab bar, this unifies the Sidebar to the vertical tab bar.
Note, this addon doesn't provide vertical tab bar. You have to make the tab bar vertical by other addons or userChrome.css. I verified that this works with following addons which provide vertical tab bar:
If you see any problem, see FAQ at first. If there is no solution, post a report to the issue tracker on the GitHub please.
Released version includes following language packs: