While the containers are really useful, the user experience is lacking.
For example the sort button has no confirmation. I clicked by mistake and all my tabs are now sorted by some weird logic and not by my context. And I cannot revert this.

An incredible and very unique add-on that lets you have multiple isolated tabs/sessions at once in the same browser. Its best feature is the "restrict to site" so if let's say I put Google search inside a container and restricted it, everytime I wanna search something in the search bar it automatically opens up Google search in that container, isolated from every other tab and from my session, it opens Google search in an contained tab, Firefox within Firefox, Fireception. This is an essential add-on to have for anyone who cares about enhancing privacy. It's absolutely brilliant and you can't find it in any other browser.

If I remove a page to open in certain container, after syncing it will come back and page will still open in that container. But I deleted page from the container.

This is the closest I've found to Chrome's tab system (super helpful for students) but I wish you were able to edit/add more categories.

Классный виджет.
Пользуюсь давно.
Косяков нЕ обнаружено за всё время))

This is Firefox's killer app