how can I add dynamic variables in email layout?

[SheltonT]

We created an email layout to set the email header & footer to keep a consistent design across notifications. 

In the email layout we added the variable  ${notification:body} for the email body placing it between the header & footer.

Is it possible to add other variables? We want to have a dynamic first line on the email layout so the email preview in outlook/gmail/etc. shows something. We tried  ${notification:subject} but when previewing the email notification the body will no longer show upon adding this. 

[SheltonT · Accepted solution]

The subject is not the same across all notifications. We were attempting to use the subject line from the notification email the email layout/template is ultimately used on as the first line of the email body as well for now.

I dont want to set the subject line as that is already being driven by the email notification. But we can try adding a mail script to the email layout/template to set the text above the header.