It would be better to choose a simpler add-on, such as the ones recommended by the Tree Style Tab developer at http://piro.sakura.ne.jp/xul/_treestyletab.html.e

It would be better to choose a simpler add-on, such as the ones recommended by the Tree Style Tab developer at http://piro.sakura.ne.jp/xul/_treestyletab.html.en http://piro.sakura.ne.jp/xul/_treestyletab.html.en, in the section “Similar or Related Extensions”. > I want a simple vertical tab, without tree features. > Vertical Tabs (https://addons.mozilla.org/firefox/addon/108862/ https://addons.mozilla.org/firefox/addon/108862/), VertTabbar (https://addons.mozilla.org/firefox/addon/8045 https://addons.mozilla.org/firefox/addon/8045) or Vertigo (https://addons.mozilla.org/firefox/addon/1343 https://addons.mozilla.org/firefox/addon/1343) can do it. Tree Style Tab has lots of bugs for me, like permanently hiding the navigation bar after I exit full-screen, and scrolling all the way to the bottom of the tab list whenever I restore a closed tab. I still use it because I love being able to organize my tabs hierarchically, but if someone only wants vertical tabs, they should choose a simpler add-on that is less likely to have bugs.