Rated 5 out of 5 stars

Very nice addon, very usefull. :-)
But, please, how can I change language?
Thank you.

This review is for a previous version of the add-on (5.9.1). 

the language of your Thunderbird version is used. So if you have installed Italian Tb, then you will see the Italian translation of QF. You can also change the language from Thunderbird using General / Language & appearance / Language. Use the "Set Alternative" button to download and activate other languages. I do most of my translations with google translate, and some of them may be incomplete, for a full list of what;s there check my github page: https://github.com/RealRaven2000/QuickFolders/tree/ESR91/_locales