Especially if you do any web development or IT, containers is great for testing different cookies. You can easily be logged in under multiple different accounts in the same browser window, which can be super useful for debugging certain issues tied to user accounts on a site. It's honestly such a useful feature that I'm shocked there isn't an alternative available in chrome, but it does also thwart tracking so I can see why Google won't implement it.

Tree style tabs enables vertical tabs, which are listed at the side of the window rather than the top.

It means you can still read tab titles when you have more than a dozen tabs open. Plus you can nest and rearrange your tabs to fit your work or study.

For some, like me, it's a game changer and I dislike using chrome now because it doesn't support vertical tabs.

Caveat: to disable top-of-window tabs you have to use a user chrome CSS file, so it's not just "install extension, enable checkbox" easy.

I don’t use containers all that much (I just auto clear cookies and history when Firefox is relaunched) but I can’t overstate the workflow upgrade that was my switching to TST a few years ago. That combined with a plethora of mouse macros for moving between tabs, changing their position in the tree hierarchy, and other basic functionality really made the experience of using a web browser more enjoyable and interesting. Lots of customization to be had with userChrome.css + TST css theming. Thankfully there’s a lot of prebuilt configs shared on GitHub to help get you started.

Containers are the best. I use them every day.

Also I switched from Tree Style Tab to Sidebery. I like it better for some reason.