Example Use Case: Banquet Event Order with Food merge fields listed in left table and beverage line items listed in right table.
First create a table that is the master table that would just have two columns. Then within the first cell/column of that table, add another table and put your merge fields in that table for the left side table.
Then in the second column in master table, add another table within that cell and put your merge fields for a different related list to merge.