There is unstarted, start, finish, deliver, accept, reject. I want to add one called shipped after the accept/reject; how is this done?
You can't; you can use tags for this, but I agree if you argue that it's not a complete replacement.
On the other hand, probably, it worths to think why you need a "shipped" estate. If this is to say that the task or feature is ready on a server, maybe it's better to leave it on "deliver" until it is. This route can vary if your definition of "done" is different, but in my opinion, something is not done until you can demo it. If the purpose is to track what set of features are currently delivered, it's better to track release versions in the code repository.