Designing proportional layout with the mouse

I'm trying to design a Morphic layout using a minimum of code. I see
that you can set the layout policy of a morph from the Yellow button
menu. Unfortunately, I don't know how to add a sub morph using that
policy.

Currently I'm positioning one morph on top of another and evaluate this
code:

parent layoutPolicy: ProportionalLayout new.

parent
  addMorph: chld
    fullFrame: (
      LayoutFrame fractions: (
        (chld topLeft - parent topLeft / parent extent) corner:
         (chld bottomRight - parent topLeft / parent extent)
      )
    )


While that works I'd like to do this the eToy like way if possible.

Alex