[Sophie]

Is there a way to do an "overlay" where objects in the upper layer can depend on objects in a lower shared layer (but not the other way around, of course) e.g. an object on an upper layer is attached to a magnet on a lower-layer object?

If you change the shared layer object (e.g. make it bigger), then the upper layer object is affected (e.g. it moves), but not vice versa.