Painting on objects after build

Can someone explain to me why UE4 can’t or hasn’t implemented functionality to where a developer can select an individual object in the editor scene and paint over a blemish they don’t like—whether an error from lightmaps, color selection, or otherwise. Wouldn’t you guys agree that would be incredibly helpful? This gif shows a perfect candidate for something like this. It’s a lightmap blemish after a recent 2-hour build . Imgflip GIF Maker

I wonder if it’s just technically impossible, because it seems too obvious to overlook.