Onihikage, 2 months ago

There are several addons that organize the tabs in the sidebar with a vertical, tree-style layout, with nested tabs that can be collapsed, just like a classic folder structure. This is what GreyBeard was referring to earlier in the thread when he said “The tabs are in a tree hierarchy”.

https://addons.mozilla.org/en-US/firefox/addon/tree-style-tab/ has been around since 2007; https://addons.mozilla.org/en-US/firefox/addon/sidebery/ is much newer, and IMO looks and performs better.