Hello
I looked at your proposition but none fit to my need, sadely.
However, I found this option MODX 3 - Dictate the template when a child is created of a certain parent - #6 by bobray
I tried it but…
… when I save the resource, the saving bar is turning for ever
If I remove it, it save the resource in 1 sec.
That option look nice, because I would be able to set the hidemenu to true, as well