Unique elements in sublists

[Daan]

Maybe this topic can help:

Remove duplicate points from a combined/ structured list

This is a tough one. As a start, take your PruneDuplicates node and get the first index of each item in each sublist with a List.AllIndicesOf node and some crossproduct lacing at level 2 and keeping the list structure. The next steps should start to unravel from there.