Introduction

Custom Vertex Weights/Normals come with the engine to provide support for mid-poly to low-poly models to use weighted normals that were done in external 3D software.

Source 2 accepts custom normals, but it is hidden away at the moment and is checked off.

Custom Normals on your model

We need to add RenderMeshMarkup to the mesh you want to apply it to:

Then we need to check "Use Expensive Tangents":

Here is a before and after: