Reason as parameter in request properties (new definition)


We are using the new definition of request properties on some of our service items. We also have "reason" as a mandatory field on the service items. Currently this means that our users must first add the fields in the request properties, then edit the object in the shopping cart and add a reason. I have tried adding a parameter named "reason", but haven't found any way to add this to the ShoppingCartItem or PersonWantsOrg- tables before the request is submitted. 

Is it possible to add "reason" as a parameter in request properties (new definition) and save this directly to ShoppingCartItem.Reason when added to the cart? 

We are using One Identity Manager 9.1.1 and the angular web portal