In this tutorial, you’ll learn how to:
• Blend two normal maps together correctly
• Add base color and roughness textures
• Control the intensity of each normal map independently
• Normalize the result to avoid lighting artifacts
• Expose controls through a Material Instance
https://dev.epicgames.com/community/learning/tutorials/L0BY/epic-for-indies-how-do-you-blend-two-normal-maps-in-unreal-engine-5-7