The fix is easy though.
Can you open an issue, I will have a look this evening :)
2/ I also defined specific nodes for a Tree model. These nodes overrode the childrenItems method to provide children elements. It looks like this method is not used anymore in TreeNodeModel. What should I now use to provide children elements in a TreeNodeModel?
You used to have Morphic node specific classes.
Now there is only TreeNodeModel.
So instead of creating a subclass, you will have to specify the TreeNodeModels you want
(and specifying children is #children:)
It is also possible that I forgot some scenarios, in this case, you can send another email,
or wait tip next week so we can sit together :)
Ben