How can I add a custom parameter to a face with Face API?

Question

Hello. I am creating a PersonGroup in which I am going to add people and faces, but I need to add a specific parameter for my project, how can I add this parameters from the Cognitive Services page?

I thought it could be added from the "Add Face" section in "Query parameters" as I show in the following image:

I also tried to use the "JSON fields..." section to add the custom parameter I need, as well as in the following image:

When I do a GET Face or GET on PersonGroup Person it does not return the custom parameter information I need. How could I correctly add my custom parameter?