I’m guessing you’re making copies of use cases via copy/paste in the diagram? If so, that’s likely the cause of the issue. When you copy/paste in a diagram, you’re simply creating another shape that represents the same underlying item. Why do we do it this way you might ask? It's is especially useful when you want to copy multiple shapes to form a basis for a new diagram, or if you’ve applied formatting to a shape (color, size, etc.) that you want to re-use in another diagram.
Instead, I think you’ll want to use the “duplicate” option which is available in the clipboard section on the Home tab, or via right mouse context menus (only applies to items in the lists and project browser, not to items in a diagram). This will create a completely new item which is independent of the original. It will be assigned a new ID and you can edit it in any way without affecting the original. The tricky part will be if your use cases have ID references to other use cases – you’ll need to manually change the references in the new use cases to the IDs of the new use cases.
Here are a couple of other ideas to consider:
1) You can duplicate an entire package instead of individual use cases. For this to work, you'll want to make sure your packages are saved in separate files (once duplicated, save the new package in its own file by right clicking on it in the project browser). Since the packages are saved in separate files, you can delete either package from your project but it won't delete the underlying package file. An advantage of this approach is that it keeps the old and new versions completely separate. If you want to view the old versions, you can import the old version of the package file(s) (best to import into a brand new project just to keep the separation of old and new). If you have a lot of packages, you might consider doing this on a per project basis and performing a File / Save As.
2) Upload your project to requirements.cc – this has a versioning and differencing feature explained here:
Requirements.cc keeps a history of changes for each item in your project every time you upload. You can view how an item looked on a specific date and get a visual indicator of differences between any two versions. The one caveat is that we are still in beta, but I highly recommend this approach. The big advantage is that you don't have to worry about ID renumbering or branching - versioning is done automatically each time you upload.
Here's a brief introduction to requirements.cc for those unfamiliar - it’s a secure website that allows you to upload and review your CaseComplete requirements. Only you can access the project, however you have the option to share your project with others by means of a password protected URL. Learn how to get started here:
Hope this helps. Let me know if you have questions regarding the various approaches.