You'll use two variables together from your list of variables on the side bar to get the line ID to show up on your export - like this: ##.
The group_id variable will give you a 1 or 2 or 3 and so on for the group number, and then the line_num variable will fill in the line number (01, 02, 03, etc).
Remember to put the two variable together in your export formula without commas in between them.
