I used Tree Style Tabs in Firefox, but it looks like it was tacked-on (because it is). Also Firefox doesn’t have a good way to hide the normal top tab bar, so y

I used Tree Style Tabs in Firefox, but it looks like it was tacked-on (because it is). Also Firefox doesn’t have a good way to hide the normal top tab bar, so you have to go into browser-chrome CSS and hide some UI elements.