Realtime collaboration on conversations

Two or more users can participate on a single conversation at single moment?

This will depend on your channel and how you configure it. For example, in Slack, if your bot is a participant in a channel, and is set up only to respond to @ mentions, there could be multiple people talking on the channel.

Sorry, I will be more specific. In conversation designer is it possible to have two or more developers working on it, in the same time.