How can I get Opportunity Title to show up in an email sent from sales process campaign?

We have multiple opportunities tied to one contact. We need to send follow up emails to the opportunity owner, but the emails are useless unless they include the opportunity title pulled from the opportunity record, not the contact record.

I know you can build an action set email that contains the ~lead.opportunitytitle~ merge field, but if I try to type that merge code into an email in the email builder it gives me an error. Is there a way to get this merge field added to the merge menu?