This UE5 tool automatically creates and assigns textures and material instances for you to paint to with the Texture Painting Tool, meaning you can, e.g., have a dirt mask in your material and paint to it right from the viewport, and paint different dirt per instance of your mesh.
This is extra useful because Nanite meshes can't have vertex color per-instance right now, but they can do this.
Unfortunately I then found out the Texture Painting Tool is broken right now making this all but useless until they fix it
But it only took me an hour or so so whatever