See forum discussion https://wordpress.org/support/topic/ninja-forms-fileds?replies=3#post-6434717

It works when you just fill in the number in the mapping.
Like ninja_forms_field_8 > u_name =just 8

The thing I would like to know if this field id can be overriden with a name, so that if you would like to add multiple forms to a service, all with let's say a phonenumber (who get different id's). That you can fill in something like 'phone' at those fields, and that you can use the value 'phone' in the mapping so it picks up all the forms at once.

Anyone suggestions on this?
@patrickvh3

Maybe as an extension? Alternate setting? Would involve plugin-specific matching.