Add a non-portal participant to a ticket

[Ken Rose]

I'm coming from Zendesk, where it was possible to reply to a ticket, and include an email address to someone who has never been a portal customer before - like the manager of the reporter. In JSM, I have the option to add existing portal customers into the "Request Participants" field, but this won't allow me to add a "cc" type of user.

Is there a way to achieve this?