443
Mozilla released a Firefox Nightly test build with vertical tabs - gHacks Tech News
(www.ghacks.net)
From Wikipedia, the free encyclopedia
Linux is a family of open source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991 by Linus Torvalds. Linux is typically packaged in a Linux distribution (or distro for short).
Distributions include the Linux kernel and supporting system software and libraries, many of which are provided by the GNU Project. Many Linux distributions use the word "Linux" in their name, but the Free Software Foundation uses the name GNU/Linux to emphasize the importance of GNU software, causing some controversy.
Community icon by Alpár-Etele Méder, licensed under CC BY 3.0
What are these tab trees? Is that an addon?
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".
Tree Style Tab has been around since 2007; Sidebery is much newer, and IMO looks and performs better.
You are correct, TreestyleTabs was my jam for years, but I have moved over to Sidebery because it performs better and has better support for containers, as well as being considerably more customizable.