For which figure? Genesis doesn’t support partial morphs, there’s only one geometry (which belongs to the root node). It doesn’t, however, matter - a morph will change only those bits of the mesh you alter, it won’t stop morphs on the unchanged parts from working normally (nor indeed will it stop morphs on the parts it does affect) - and you can place the controller on whichever body part you like if the root is not a logical or convenient location.