I cannot get these two to appear on my receipt forms, no matter where I place them on the HTML.
Those variables are not part of the receipt form. There is only a Payer.
How can I get my client’s identifier and address on the receipt form?
You could do this only with custom fields and a bit of fancy custom theme coding.
But custom fields don’t appear below the client’s name. Could you help me with the HTML?
No, I can’t. That’s why I said it would take some fancy coding. I’m not a programmer. And by the way, custom themes are written in Liquid.