How to set shade smooth of skeleton mesh assets in the engine?

Recently I have been working on the Non-Photorealistic rendering effect. I found that the outlining effect of the shade smooth model through VertexNormalWS has continuous lines, while that of the shade flat outlining is not continuous.


Because I still need to do the shading processing for Non-Photorealistic rendering, I can’t handle all the models with shade smooth. Although I can make both smooth and flat versions of the same model, but it would be very troublesome.

So, what methods can be used to make changes to assets in the engine? It would be best to do it in the blueprint or materials.