Rated 5 out of 5 stars

Nice app, very useful. I have a question Is it possible to integrate "Extension option " menubar to "Add-ons" menebar in Thunderbird?

This review is for a previous version of the add-on (2.0). 

It's not currently easily possible. When Firefox got the title bar menu, Mozilla added a menu type called "splitmenu" that makes that possible. It's not in Thunderbird yet. When a title bar menu is added to Thunderbird, I will add the option to this extension.