UPDATE:
I really need the containers to be grouped (for easier access and management), manually sorted and bookmarked with container information attached to be easily restored.
I am developing a web site. I have test users with their roles on site. For each user I created an individual container. 6 roles require 6 pages to be restored every time I reload the browser. I want them be restored automatically in their respective container at the time when the Bookmark was created. One site, several bookmarks with individual containers for each test user/role.

ORIGINAL REVIEW 2 years ago
I used to open Chrome for one Google account and Firefox for another. To check business emails on Gmail and to view videos on YouTube, for example. It consumed quite a lot of resources on my old Dell Vostro 3700. Now, I can manage all my "personas" in Firefox alone, which I personally like more.

But, the new "problem" now is it's hard to find necessary tab on Windows task panel. So, I suggest, that not only individual tabs can be marked as containers, but every FireFox window could be assigned a default "persona" with different coloring and EVEN logo (I like the Fox, but sometimes it'd be useful to have those personalized icons to faster localize necessary tabs). PS. I use A LOT OF tabs (up to 50 in one session, I guess). So, saving time trying to locate a necessary tab would be cool.
On the whole, this is a really cool feature which is worth taking time to understand how to use. Firefox, please make a new button - Learn the Feature - so that it would be like an ed course with games, videos and tests (reading is boring and confusing, as you know).

"Limit to Designated Sites" checkbox keeps being unfilled automatically. This has happened multiple times, even right after I enable it and go back to the previous menu

Best add-on ever

its should be move containers in edit mode!!! i told it weeks ago!

Works as expected

Junto con "Cookie Autodelete" y NoScript, mantiene los sites aislados y limpios de paja

Recommended because it's made by mozilla. Does not install, corrupt file error message. Why you recommend an addon that you have not tested?

On the one hand, I very much like the idea, and often this add-on works great. On the other hand, I have a need to open tabs for https://domain.org AND https://subdomain.domain.org and there is no way to get both of these opened into the same container. The emails they send me link to subdomain.domain.org - and I'm not logged in there, because they are in a separate container.

This is a brilliant add-on. If you happen to use multiple accounts for work and home for example, you can set this up to open work related pages in work tabs and avoid the annoying switching accounts. It also has the Facebook container that helps stop them following you.

It is 2020, still cannot sort the list created.