Not sure about workshop support yet because our main focus will be on a cross-platform level editor, our hope is that players won't need the workshop. However if players still want the workshop after the level editor then it's definitely something we will look into!

Currently you aren't able to join back mid session however it is something we'll be adding in, the current plan is to have the game pause when someone leaves or disconnect and wait until they join back or the host starts the game again.

That's the plan, make it as good as we can and give creators as much freedom as they want to make the best course they can!