A new tool (capable of the creation of more complex data models) is available at the menu “Draft a data model”.
It is an external tool that simplifies the json schema needs.
Hope it speeds up the development of new data models and simplifies it for newcomers to this syntaxis.
Anyhow this is the best guide (simple and straight to the point we know)
It is also available at the learning zone in the upper menu.
The JSON schema is our single source of truth compiling into a single document the technical description with the definitions of every element in the data model.