Thanks for updating the thread.
I am slightly confused with this. Can you please elaborate?
However, let me try answer as per my understanding. Elementor Page Builder has templates system, if you meant that using Elementor Page Builder contents imported using it's templates into Cornerstone, unfortunately that's not possible.
In case you are referring to Cornerstone templates, sure you can use that but before you need to create contents using Cornerstone.
In case I misinterpreted you question, please clarify and we will be happy to assist you.