You should set this as a Product Idea to enhance development environment when working in groups. It is a know issue. Biggest problem is in Manage Field/Tables/Relationships, there there is so much better to do a GUI-file and a Data-file so that different developers can work on different areas.
But as I sad, it's not longer a problem in Filemaker 15. I haven't tried earlier versions, but I think it's more about the new script workspace.