So I just got back from Unreal Academy Enterprise and learned something interesting:
Did your tutorials release before this node became available, or did you just do it as a learning experience? (Which is still great, because I’m completely clueless about these things, yet was able to follow along your explanations, which is amazing because I haven’t managed to understand anything this advanced before I saw your video!) 
EDIT: Noticed I had 2 likes on this, so I updated the picture with the WorldAlignedNormal node as well, which was missing before. So please note that normals in triplanar behave differenly!