Sort AB List into A's and B's

How does a list get sorted like this?

Member Index on a Set of a Set is recommended, not to be confused with Item Index

Thanks! How does that then get broken into two separate panels?

Once you get it into a Trees you can use tree branch to isolate a branch.

Note that if you have more than 2 values and use the explode tree you can right click and Match Outputs, or zoom into the ZUI and add the via the +

This is a very slightly different approach, just using the output of the Create Set component to feed back into Member index. This way you dont have to create a separate list with the unique items in the first list, that you want to search for.