Hi Sven,
Aside from saving them as blueprints, you have to upload them to Steam Workshop as well. When you go to My Blueprints, then hover over the creation you want to upload, it should give you the Steam Workshop icon. Click on that to access Steam Workshop and upload your blueprint directly. Your Steam friends and other players should then be able to see your work.
Let me know if this worked!
Cheers,
Bo