We have added preliminary support for Steam Workshop with this update. You can share your creations in-game by going to options -> share.
Once you subscribe to a shared creation, you can load them in-game like a standard save file.
As part of this, we have also uploaded builds for the game's 12 built-in blueprints, as well as a new blueprint, "Inline-4 Engine", which is a simpler piston engine.