Adding a geometry shader to a custom shading model

Hello everyone,

I am trying to add a geometry shader to a custom shading model, but I am struggling a bit.
It does not seem like there are a lot of examples out there.

I am using UE 4.24.3 and added my custom shading model by following this tutorial Unreal Engine 4 Rendering Part 6: Adding a new Shading Model | by Matt Hoffman | Medium and adapting for 4.24.3.
At the bottom of the tutorial, it said that adding a geometry shader would come next, but it seems like it never did.

Any pointers to examples/tutorials would be much appreciated.