It's probably the wrong folder again. They go in the GalaxyForge folder that is located where the mod/saves/setting/screenshot folders are. They will then show up in the "Galaxy Forge" tab in game, not in the normal tabs where all the other maps are.
I'm afraid I don't have Windows 10 yet nor do I play Trinity/use galaxy forge 3 anymore, so I'm mostly just going from memory on the old days here. 