Hi, all - a common question we get from admins is if we have a comprehensive list of Mail Merge Variables for Email Templates for Automation Rules. The short answer is that we do not, due to the amount of merge variables there are, and how quickly they change. This has been an internal conversation for a long time, but a good rule of thumb is that the available mail merge variables will display based on which template you're in, and can be accessed by clicking on the following button in the HTML editor when you're formatting the Email Template:
That said, we do have a list of our Events Email Template variables that have been compiled, and it's available here. While it does not detail the purpose of each variable, it's the most current list of what variables are available for each type of Event Email Template.
Please note: merge variables must be included in the email exactly as they are listed; any changes in the syntax of the merge variable will result in it not populating.
Hope this is helpful to you all - have a wonderful day!