Wolkom by Thunderbird Add-ons.
Foegje ekstra funksjes en stilen ta om Thunderbird hielendal fan jo te meitsjen.
SluteOer dizze add-on
1. hamburger menu
2. add-ons
3. click on TabAddressbook
The customize menu is obsolete for this add-on.
This is a hack from mthaens "Addressbook in Tabs" for TB 60.