Thanks for the reply, but I'm not sure this gets me where I need to be. You are correct, I miss spoke on which list would be the parent, L1 to L2, but I think you get the picture.
I do in fact need to identify in one list, lets say L4, each level of the hierarchy within that list. The Boolean was just as example of what my real goal is. I am importing data into 4 separate line items, each one applied to a level in a hierarchy.
L4, L3, L2, L1.
I need to combine all the line items into one line item that is applied to L4, using summary as Formula, I need to say if item is L4 then pull from the L4 line item, else if item is L3 then pull the L3 line item, and so on.
I had a hard time trying to get my example written down with it not confusing anyone, so I went with the boolean example instead. I may have still only confused you on what it is I'm actually trying to do, but Jared's approach worked for me. Maybe there is another way that might be quicker but for now its all I got.
Thank you both for your thoughts on this! It's definitely expanding my knowledge.