Very lovely addon though there are some possible tweaks.

- adding temporarily tabs which doesnt belong to any container and will be deleted after closing the browser.
like opening a link as a contained tab.
- It would be nice to be able to change the order of the categories.
- Also instead the whole domain it would be nice to categorize just specific subdomains or paths e.g. "test.com/news/*"

besides that, as already mentioned very lovely!