[otrs] Guide to customizing responses, auto-responses etc

Is there detail info someplace that explains all of the option available for this? I really want a list of the available variables, but so far have found no documentation. For example, when I set a ticket to pending, I would like the notice to the user to indicate the exact date/time when the ticket will close. Right now I'm using the "status change" notification method for sending the user a notice, but would really like to include more info on the response. Thanks Jeremy P