Rated 2 out of 5 stars

@Harry, Yes, I've had email open on two computers, also, though I don't know whether it might create a security warning from the provider, or just synchronize the accounts.

This review is for a previous version of the add-on (1.1.1). 

Rated 3 out of 5 stars

@Harry Yes, I simply installed an older version of Thunderbird overwriting the newer one, then after sorting the folders, I updated it to v 60b11 (current) again. This works with portable Thunderbird also. I have two separate groups of mail accounts, one in portable TBird, the other installed. since TBird allows only one (open) instance, profile conflicts aren't a problem. (Unlike Firefox, which will corrupt your user profile if you forget to close one.)

This review is for a previous version of the add-on (1.1.1). 

Rated 2 out of 5 stars

Reverting Thunderbird to v56.0, sorting the folders -- then updating Thunderbird -- is a work-around, until the add-on gets fixed.

This review is for a previous version of the add-on (1.1.1).