Hi Peter,
maybe you can help me. I'm still missing one point, and I can't find, where I have to change this. I like your guide, although it didn't have a solution for my problem 
After adding the custom message widget, it appears correctly in the "Home" screen, and also in the available Assignment blocks. But the title is missing, and I don't know, where to add it.
Do you know, where I can change this?
Thanks and best regards
Daniel