Nicks IRIS Theme Banner Image with stacks?

Hi I bought the Iris theme von Nick Cates.
Almost I use stacks. But now i want to create a banner image.

But it dont work with stacks . Is it normal or did I make a mistake ?

In the manual stand
Dop the image, richt click and alt tag “edge banner”.

But this dont work in stacks.

Can someone give me a advice ?