BP has never had the capability for multi-user editing, and in my experience most of the time this is not much of an inconvenience. I agree it would be a 'nice to have', but consider the difficulty in merging a diagram that two users have edited - if each user radically changes the layout, what would a merged diagram look like? We did give this a lot of thought in the early days but soon realised it would be a recipe for trouble.Design can help a lot with collaboration: rather than create a single 'mega' object, it's better to create a series of small objects, each one focussed on a particular screen or function of the target application; a solution can also be formed of multiple processes, simplifying the development, and crucially, the testing.