The y coordinate isn't shown for every feature. For structures that always generate on the surface or seafloor, this shouldn't be an issue. In other cases, like mineshafts, strongholds and nether fortresses, the structures can easily be found by searching at different heights at the given x...
Full-World Map: Instantly view your entire Minecraft world, just like using Google Maps, but in-game! Biome Finder: Quickly locate biomes of any type and plan your next adventure. Structure Discovery: Easily find villages, temples, strongholds, nether fortressess, and more. Custom Pins: Mark...