I guess I found a bug in Browser>openAsMorphClassEditing in my Version there was window addMorph: self buildMorphicMessageList fullFrame: ((0.5@0 corner: 1.0@hSepFrac) topOffset: switchHeight).
I had to change it to: window addMorph: self buildMorphicMessageList fullFrame: ((0.5@0 corner: 1.0@hSepFrac) asLayoutFrame topOffset: switchHeight). Otherwise I get an MNU for Rectangle topOffset: I guess I've to figure out on how to send proper patches to this mailing list. Regards Friedrich