In the discussion of transitions it points out that you have to define a transition for each mapping. Not really sure why you'd ever want to do that in most applications. In general you'd want one transition that impacts everybody and, perhaps, override the default for specific cases. To this end Magellan needs to expose the ability to set a default transition that applies to navigation except when specifically overridden either for a specific mapping (such as to an error page) or programmatically via the API.
Someone posted this in the feedback for the article and you mentioned that you'd try to post a simple implementation but I haven't seen anything since then.
