Nicest UE GitHub contributions we have to thank our community for?

Thinking about Godot (and Unity's closed code if we ignore Packages/Assets), I just wondered...

Q: What were some of the most amazing or helpful (Editor?) contributions so far in Unreal Engine 4 and 5?

...especially those that landed in UE4 / 5, part of the engine features & fixes.

I'd like to understand a bit better how large and complex the undertakings and possibly (Epic's) reviews and QA were... although here we'd have to guess a lot anyway.

And maybe how Epic Games deals with the code ownership of something that (in theory) could get more complex, get rewritten, slowly integrates into one or two other modules (e.g. a feature now supports animation to some degree).