The abdomen's WaistWidth is linkParmed to the BODY WaistWidth, so they should be the same always. But the WaistWidth does not only alter the abdomen, but e.g. the hip, too. So one method to get the WaistWidth into the hip, is to put a child morph for the WaistWidth in the hip, this is what they did (abdomen linked to BODY, and hip child of BODY). They could have made the hip a child of the abdomen (for this morph), but if they would do something like this for every morph, nobody would understand the interdependence of the various morphs anymore. An alternative would be to only make a full body morph for the waist width (in the BODY), and make the abdomen's morph a child of it, but then you wouldnt find the WaistWidth within the abdomen (this is where everybody would expect it to be anyway). So the general strategy seems to be: Put the main dial into the body part where it you would look for it, copy the value up into the BODY, and then let other children depend on the this. Perhaps not the best way to do it, but at least not too complicated.