Dear itemis team,
I think it would be immensely helpful for newcomers to the new GEF if you provided another part of the tutorial, showing how to embed the mindmap application in an Eclipse 4 part. A lot of devs will come from Eclipse 3.x GEF and will want to create an editor in an e4 app, either using an MPart or bridging with extensions and using AbstractFXEditor.
Or perhaps provide a minimal example in the GEF GitHub wiki?