new Thunderbird, how do I change a recipient from 'cc' to 'to' ?

I guess I got a new Thunderbird with the latest Leap 15.2 updates? from 68 to 78 ? I know it sounds stupid, but I simply cannot figure out how to change a recipient from 'cc' to 'to' (or vice versa). In the previous TB, there was a pull-down menu, that seems to have gone away. -- Per Jessen, Zürich (5.6°C) http://www.dns24.ch/ - free dynamic DNS, made in Switzerland.