The following tags can be used to add content dynamically:
[from_name] - Attendee name
[from_email] - Attendee Email
[meta_data] - All custom form fields in list format
[registration_id] - Registration ID
[user_id] - User ID of attendee
[event_id] - Event ID
[event_title] - Event Title
[event_dashboard_url] - URL to the frontend event dashboard page
[event_url] - URL to the current event
[organizer_name] - Name of the organizer which submitted the event listing
[organizer_email] - Email of the organizer which submitted the event listing
[date_of_participation] - Date of attendee checkin
[event_post_meta] - Some meta data from the event. e.g. [event_post_meta key="_event_location"]
All tags can be passed a prefix and a suffix which is only output when the value is set e.g. [event_title prefix="Event Title: " suffix="."]