I faintly remember reading somewhere that the landscape system calculates a normal map from the height map to be used on the terrain (is that correct?). However, I have normal maps (from World Machine) that I would like to use to increase the appararent resolution of the terrain. Can I do this? Would I simply assign them to the normal slot of the material (using a terrain coords node for correct UV mapping)? Would I have to merge those terrain normals with the normal maps that come with the detail textures?
Sorry for bumping this, but I’m really interested in an answer 
If I wire my normal map texture (generated in World Machine) to the normal port of my Landscape material, the shadows get way too pronounced. I guess UE4 creates a normal map out of the heightmap (by finite differencing or so) and uses that, anything wired to the normal output is added to the internal normal map? Is there a way to bypass that? Also, the docs state that
" In addition, the full-resolution normal map of the Landscape is available. "
How? Thanks!
Yes you can. See the tutorial below for how.
Copy/pasted from another World Machine question I answered 5 mins ago.
This is a step by step tutorial. Worked perfectly for me.
Step by step for everything except the splat map creation, for which world machine has an example.
Yes you can. Just plug a landscape coordinate node to the normal map and set the UV scale to the size of your landscape.