Linking boards which do not have a direct relationship via automation

I have several boards which I move information to once tasks are complete. Information moves from board 1 to 2, from board 2 to boards 3 and 4, from board 3 to boards 5 and 6. I know how to link these boards (by automation) but not sure how to link, say, board 4 with board 6 or board 2 with board 6, for example.
The recipe might be “When an item is created in this board, connect the item where this column matches this column in another board by this logic” but not sure what this means. Can you help me?