Adding custom shading model

I’m looking to add a stylized lighting model to my unreal project (version 4.26). I’ve found these tutorials on how to do it but they’re for an older edition and some of the code has changed too much.

https://web.archive.org/web/20210514075420/https://blog.felixkate.net/2016/05/22/adding-a-custom-shading-model-1/

I’ve been able to modify an existing shading model to give a different result, but I’m struggling with adding a new option in the drop down menu. Any help would be very appreciated, thank you.

I’ve found another tutorial here: Exposing the BRDF Models to the Material Editor? - #7 by anonymous_user_c28e91fb

But the main problem is that where the MATERIAL_SHADINGMODEL_* are set have changed location and I can’t find the new one. Does anyone one know where it might have moved to?
Thanks