How to set Title in Contacts but not display it? Is there a way to set the 'Title' field in Contacts, but to not display it?  i.e., in Mail I want to see "John Doe", but have the contact card display "Captain John Doe".

Can I do this?
Set it as a Nickname instead. Then it would only be seen by you.

Don't hand the contact card to anyone, though, as it would be in that.

See Does a Contacts Nickname transmit to anyone else; iMessage or email? for a cautionary tale ;-)

A friend of mine has been "Young Master Johnson" [fake name] for 15 years without anyone else knowing.