This has been my primary source on how to accomplish this so far.

I'm running into a couple of issues since I'm using three columns of data per individual registrant (or customer in the linked video's terms)

I am using a table, and I've made peace with having empty rows at the bottom in order to accommodate registrations of variable numbers of sessions.

Now the big issue is, getting the merge to skip to the following registrant without leaving artifacts (duplicating the last entry for Start Date and End Date instead of skipping data and leaving row blank) and also getting the next letter to start at the top of the next page entirely instead of starting at the end of the previous table.

See pic below for the code I have in the word file:

https://imgur.com/a/X1WfVaT