At first I thought that this was like tab groups. It really isn't. Multi-Account Containers are all about privacy. And sure, you can have two different Container tabs with different Whatsapp accounts, for example. But for me it's much more about keeping Google's prying eyes away from all the other stuff I am doing and minimizing my social media footprints.
This add-on could be your only reason to start using Firefox if you aren't yet.

The only two things on my wish list for this add-on are 1. more icons to choose from (or just using your own icons) and 2. more colors to choose from (or just entering your own color codes).

This is the main reason I choose Firefox over Chrome and Safari. Is is so amazingly useful to manage work and personal accounts. I completely love it!

I huge thanks to the devs and maintainers. I would gladly pay for this had it been possible.

This is by far the most useful extension for any browser and is the primary reason I use Firefox over Chrome, Safari, etc. It is particularly useful when trying to deal with multiple Google accounts where you might want to access Google Docs from multiple Google accounts simultaneously. Thank you from the bottom of my heart to the developers and maintainers of this extension!

Amazing add-on. One of the main reasons I'm here using Firefox instead of Chromium-based-browsers. Hope it never gets unmaintained.

Occasionally ends up opening "ghost" tabs when opening links from Google. Also sync doesn't work well across devices and some extensions don't play well with tabs opened in a container, but overall, functionality is good.

Needs more color/icons for the containers, and I can't for the life of me get the syncing ability to work across other instances.

It's a great addon but please add a way to manually add URLs to open in a container, sometimes websites do quick redirections between domains (see Google) and it's impossible to add the redirecting domain to the container! Also wildcard support for manually added domains would be great (eg: *.google.com). Thanks!

"Hide and Show" feature is advertised, and I selected and installed the Add-on exactly for this use case. Now I can't find the feature. Can you please point me to it ?
See 2 "discussion" on this page related to the feature. My Conclusion: Falls short of this advertised use-case. Rating down for the time being until the discussion brings a solution to the restrictions.