Hi! Multiple people can't work on the same map at the same time. That's next level :) However you can share your map with your friend and take turns, by copying the UGC folder of your map and sending it to him. Or you can both work at the same time one different versions of the map and implement the best parts on one map. Good luck!

Hi! Is there any plans in the future (near or distant) for there to be a cooperative function for workshop building?

Hi. For the near future, probably not, but we might consider it in the distant one.