I know that you can select from a list, groups from plasma “search & launch” - but is it possible to create and add other groups. Also is it possible to change the kmail at the top of the display to thunderbird, which I use.
Unlock widgets
You can delete kmail when you hover over it, see the red minus
search now for thunderbird, hover over it and see the yellow star… click it
Ahhhh - Thanks caf4926
No worries 