Well MIndjet has decided to put it somehwere else.
Don't know why.... but here I found it. You have created an orgchart. Select the top topic, or any topic where you want the children to be orgcharted as well. Go to the Format tab. Select the Layout (second from left) and click the twistie. And now you see what you were looking for. including Org-Cart Depth.
I have not decided if it is just a matter of getting used to or worse ;-)