@Mike_callow of course! I’m happy to answer any and all your questions 
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In this case, I would recommend using the column_values query to find all of the column values for all of your items on a board. This will then return the subitems’ Ids.
You can then use one of these subitem Ids to query the subitem board Id, and then from there, query that subitem board to find the column values for all subitems on that board.
The manual part comes with matching each subitem Id with the parent item you had queried first.
It might help to check out this thread too!