Rated 4 out of 5 stars

Hello,
I also think there is a real performance issue in the latest QuickFolders release.
Mozilla Thunderbird may now need up to 30 seconds displaying "Initializing QuickFolders" before becoming operational.

This review is for a previous version of the add-on (5.11). 

there are some problems with the folder iterator, in Thunderbird 102, we and Thunderbird Core are aware of the problem. see issue 283:
https://github.com/RealRaven2000/QuickFolders/issues/283

I recommend using the latest version from there to see if there is a difference.

there will be more improvements in QF code itself but I am also hoping that Mozilla will fix the caching issue reporred in bugs 1773822 and 1776280.