About creating a document!

It is possible, when creating a document, programmatically enable the users Relationship function ??'

you mean relate to the User? No. you can't relate to the user. People typically create a collection named something like profiles and then make relationships to that

Exactly, relate to the user programmatically.(dynamically).
I can do it manually, but I need to create the document and relate to the user at the same time (from my app)

and all because I am reading the json of the parent Document, so that it lists everything related to it.

yes