We would like to create a LIghtning template for checking on a quote with the customer. The options for merge fields include Recipient. So we chose First name and it looks like {{{Recipient.FirstName}}}. This is the error message:

We don't recognize the field prefix Recipient. Ensure that you are using an associated record when sending the email.

It looks like there are these choices for mail merge fields. Recipient, Organization, Sender, Quote.

When we populate the email field with the sender's email (in a test) all the fields populate but, of course, with the incorrect First Name

What am I doing wrong?