It seems like hard work and requires a lot of skill to make it look like that, but I’m happy with something along the lines of that, you know, as long as it is somewhat realistic.
You could use Dynamic Material instances to do that. With the Dynamic Material Instance you can change the material in your BP.
Example when your character is under 50% HP the scars getting activated and the normal map and texture is changed or you can Lerp it with.