Adding a second but different customer email (not in case object)

We are using create as a base for a forms system. I have been able to set up emails related to the ‘case’ object absolutely fine (for both records related customer recipients and fixed recipients for our internal staff/departments), but I’m struggling to figure out where/how to add a third email recipient that is collected on the form (data capture page).

Below is the example of a working customer email we have set up
customer emails

Oops, I have asked the same question.