Hi @Frank_J,
There’s a basic set of {$variables} available to any email template, an additional set for submissions (that’s common to both OJS and OMP), and an augmentation that’s OJS-specific. Beyond those, each template might have additional ones, which can be seen in the default template text.
If you need to go beyond those, you’ll need to work with the code that’s responsible for sending that particular email.
Regards,
Alec Smecher
Public Knowledge Project Team