I would LOVE to share how I did my trees! This is an article for a very similar method to what I used. The major difference is that, instead of making a mesh of 3 intersecting quads, I actually projected the quads of the leaf mesh as billboards through texture coordinates in unreal engine similar to the method here. The branches and trunks are just cylinders without the ends capped. The ends of each branch point up and away from the player and rather small so you can't actually see that the ends aren't capped. Finally, while I didn't actually finish my global wind setup, (I wanted to set it up so that it changed direction from time to time), here's a method I love using for global wind as well as a very nice way of setting up a wind sway material for the trunk and branches in unreal engine.
I do want to say though that not all of the trees belong to me. We ended up using an asset pack to increase the tree variation (You'll have to ask Dazalius what the pack's name is because I can't remember). However, I did end up modifying the textures and materials of the trees to further match them to my own trees. The massive oak tree in the middle of the valley is the most noticeably different. The moss texture on the base of the trees and the tops of the rocks is my own hand painted moss texture set as a world aligned texture that uses texture coordinates and world position offset to color only the bottoms of the trees and the tops of the rocks.
Thank you so much for noticing our work, and I hope you follow us for future games! <3