[Hint] Complete the Set – 10 October 2022

The puzzle Complete the Set came out one week ago today. Quite a few people have solved this one, but if you don’t know where to begin, check out the hint below.

Skyscraper Stories is the new puzzle for this week. I hope you’re ready for some stairs.

These letter strings are made up of two members of a set of three, interlaced. You want the third member.