In this new community-made Making Of tutorial, Luca Rodolfi, a 3D enthusiast and Twinmotion power user shared his process to make this green canyon in Twinmotion from scratch with just assets from Quixel Megascans and Archmodels.
https://dev.epicgames.com/community/learning/tutorials/j4KR/unreal-engine-making-of-a-green-canyon-in-twinmotion-twinmotion-tutorial