Collaboration - Lock Checking Idea
In regards to prototype locking when collaborating with other users. It would be nice when closing JustInMind that the user is prompted with an alert showing them their currently locked elements. Giving them the option to commit, or discard their changes on elements that they wish to unlock. This would avoid the following scenario from happening:
A user that has been modifying elements all day and goes home without committing his/her changes. These elements would remain locked where other users cannot access data when they desperately need to make one last change on elements the other user was working on. You would not be able to make these changes as the user has them locked, the only way would be to remove the user from the prototype, losing their changes. If the user that went home was the project owner then they wouldn't even be able to do this.
If JustInMind prompted the user to commit changes (which would unlock the elements) this situation (and many other similar situations) could be avoided. I'm sure you would find that this situation would appear more than one would think.