Me, unthinking: "I'm going to make a tiny change to this Unreal Engine editor plugin UI"
Slate, waiting for this moment for years: "Ha. Ha. Ha. Welcome back to the pain, motherfucker. You want to update something? How about no?"
It truly is the worst fucking UI framework I have ever had the misfortune to interact with in decades of doing this, and I started back when there were no fucking UI frameworks at all.