This is very handy when using multiple O365 accounts. Love it.

working great with multiple email accounts

I gave you five start

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-----> CAN BE IMPROVE IT :(
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BUG ---> Why always for a new version of firefox I have to set up the plugin even when I have firefox sync activate.

1. Missing --> Not working for Firefox Focus or Firefox Android you have 366,285 Users for sure many of them use android, and there are no plugin you will be the first . Hit first hit twice ;)
why don t port to firefox focus or firefox android or even better integreated with firefox by default

2. Missing --> Better configuration I recomend containers helper https://addons.mozilla.org/en-US/firefox/addon/containers-helper/

3. Missing --> in every firefox version the multiaccount containers icon it desapear from the menu bar

4. Missing --> containers in sidebars https://addons.mozilla.org/en-US/firefox/addon/container-tabs-sidebar/

5. Missing --> Not working in private mode, containers is great to open the same web ex gmail in two cointeiners in the same browser
so I can read work and house gmail but in priveate multi account container doesn t work

6. Missing ---> Automatically open websites in a dedicated container. Simply add rules to map domain or subdomain to your container.
https://addons.mozilla.org/en-US/firefox/addon/containerise/

7. Missing ---> Temporary container option https://addons.mozilla.org/en-US/firefox/addon/temporary-containers/
8. Missing ---> Option of container proxy https://addons.mozilla.org/en-US/firefox/addon/container-proxy

If you disable this add-on then your customizations to existing containers will be lost and any new container you added later will be deleted.

UPDATE: Firefox just (13/2/20) added the sync functionality in this add-on which let's users sync customizations. Will give 5 stars if they also add the functionality of limiting a container only to assigned site(s).
UPDATE 2: They added the functionality. Giving 5 stars now.