Hi Nick,
Adding edges to established node types is something quite common in dgraph (and other graph databases). But there’s a distinction to be made: 1. defining a new edge and 2. assigning values to that new edge.
Say, for instance, your application has a Movie type with an [Actor] edge. Later you want to add a [Director] edge. No, problem — just update your schema with the new edge. Of course, at that moment all the existing Movie nodes will have empty [Director] edges. You’ll need to go back and update those nodes with the correct data.
Did I understand your question correctly?