Event Reminder Emails Pulling in Multiple Name Fields

When reminder emails are sent to participants for booked Learning Events, the reminder emails should first pull in the [Preferred Name] field, and if no information is on record, then pull in [First Name]. Currently, our setup is for the reminder email to pull in Preferred Names into the email greeting to that it reads "Dear [Preferred Name],." This provides the substantial benefit of using employee's preferred names over legal names, when they're different.

However, for the many employees that have not entered a Preferred Name into the system, the email reads "Dear ," with leaving the name blank. It would be ideal to have a way for the email template greeting to first pull from the Preferred Name field but then to use the First Name if no Preferred Name is entered.