I was recently collabing on a project with someone but we didn't have an easy way to both share it together without two projects being shared.
It would be amazing if scratch could add a way to easily collab on a project. It would encourage sharing ideas and would make projects fun instead of trying to find an artist to help with your game.

when green flag clicked
if <scratch adds this as a feature> then
say [YAY!!!!!!!]
end

they have said in the past no they will not add collabing because people could say inappropriate things to each other in like comments or whatever and it could lead to private communication. while it might sound silly, it is what it is. but to answer your question clearly, no there is no easy way to collaborate.

Have you tried making a studio where you talk about ideas? Or a remix chain where you add on to the project you’re collaborating on?

Collaboration is definitely possible; communication is key.

Basically just make the project you want to collab on, (and make sure to state who it is specifically meant for) and let the other collaborators remix and share, remix and share, etc…