I am running Thunderbird 115.13.0 (64 Bit) on a Mint 22 OS ... & have spent most of the day yesterday & a couple hours today to find the solution to the SMALL FONT SIZE in the "Folders Panel" in Thunderbird" & have checked several threads of others having the SAME PROBLEM ... ** I FOUND THE SOLUTION TODAY!! ** i simply want to save a ton of people the grief that I went through to solve the SMALL FONT SIZE in the various panels in Thunderbird ... SOLUTION: On the Top Right of the Thunderbird Screen ... CLICK ON THE THREE BARS ... and you will notice that The SIXTH ITEM DOWN IN THE DROP DOWN MENU ... IS "FONT" ... THIS is WHERE you solve your Font Size Problem!! Simply click on the (+) sign to increase the font or click on the (-) sign to decrease the font size!! Viola!! Problem Solved!! I read where people were directed to the config file under settings and setting up a chrome file ... but you don't need ANY OF THAT ... you DO However need to make sure that in the config file that it is set to the default setting of (-1.0) if it isn't ... & all of us need to apologize to the developers for saying that this updated version of Thunderbird is bad programing ... Because It Isn't!! They gave us a SIMPLE MENU to fix the font size ... we just didn't know WHERE it was!! Blessings ... I hope this helps a ton of people with the same problem that I had so you DON'T waste a bunch of time and/or stop using Thunderbird because it is the BEST Email Program Out There!!