I am trying to implement the below with fire fox containers however I am not sure how you disable the option to clear cookies per container ? See below. I also use this extension in order to have quick access to all of my Google Voice numbers. I created a new container for each Google Voice number I own. I then logged in to the appropriate account for each container and disabled the option to clear my cookies upon exit. Today, I can launch Firefox, select the container titled with the number I want to use, and immediately place or accept a call via my desktop. I can close the browser completely when I am done. I also changed the icon and name to reflect this purpose. This has been most beneficial when I have been on a call with a financial institution and they want to call me back at a specific number which they have on file. Opening the browser and being immediately ready is better than connecting to Google Voice; opening my password manager; inserting my credentials; providing 2FA; accessing the account; allowing my microphone; and accepting the call. My device is encrypted and protected with a strong password in the event it is stolen.