How to define a JSON inside body of EXTENDED API INFORMATION

Hi,

I have define this JSON inside the body:
{
"process_template_uuid": "beb199ff-41b1-456d-b197-7010659da350",

 "submission_elements":
      {
       "nombre": "[attribute=nombre]", 
       "departamento": "[attribute=departamento]", 
       "email":"[attribute=email]", 
       "consulta": "[attribute=consulta]" 
       }

}

All goes rigth but Seliom send the literal not the field value.
For example, send [attribute=nombre] instead of Ignacio Fernández.

This is a video explaning all the porcess:
https://www.loom.com/share/8d1772be49574ecdaef5a5765e641e1a

My question is how do I have to define the attribute within the JSON so that it sends the value of the attribute?

Many thanks,