In version 12CE:
I have a model with a one2many field. This field itself has a one2many field inside it. 

In a form view I have the initial one2many as a tree. However, within this tree, I cannot load the second  one2many field as a tree. 

Is there way to put a one2many tree within another one2many tree view.

It works well on the frontend website but I cannot get it to work in the backend.