WorkspacePro might be a bit more popular than Tree Style Tab. We know about 1 link to it since March 2021 and only 1 link to Tree Style Tab. We are tracking product recommendations and mentions on various public social media platforms and blogs. They can help you identify which product is more popular and what people think of it.
Tree Style Tabs were released for Firefox around 2007 https://piro.sakura.ne.jp/xul/_treestyletab.html.en#history I am not sure if someone was earlier, but Arc is copying this. - Source: Hacker News / about 1 year ago
The three main options I can think of are Workspaces mentioned above, another app by the same name, and Workspace Pro. Source: over 1 year ago
Tabs Outliner - Next Generation Session, Windows, Tabs Manager and a TooManyTabs Solution That Really Works.
Workona - A better way to work in the browser.
OneTab - Whenever you find yourself with too many tabs, click the OneTab icon to convert all of your tabs into a list. When you need to access the tabs again, you can either restore them individually or all at once.
Session Buddy - Manage Your Browser Sessions
Multrin - Organize multiple apps in tabs
Sidebery - Manage your tabs and bookmarks in sidebar.