I don't know about you, but I think you can't replace files with this. But you can export them or make a new file containing them. [sdat, nds] [ed: it's been confirmed, you can't.]


How about adding  Freeze and  ray's Worldmap Editor? It is a little complicated to use for some people and it's still in beta, but it is quite a nice app.


Edit: Outdated. See NSMB Worldmap Editor for current progress.