Here is a short video how to build custom levels for Commander Cool. The documentation is still alpha but this video gives you a great start how things working.
https://www.youtube.com/watch?v=Iy3Vi-3VwxQ
We are working hard to create a seamless integration with steam workshops but this will arrive in a future update. So for now you cannot share your maps via steam workshop.
if you have any questions please feel free to contact us anytime :)