In regards to Maggie LeFay's "Way Stone" (for lack of a better term):
It's said a few times throughout the series that where the Nevernever touches the mortal world changes as the mortal world changes. I also recall in WK it's implied that the person creating the 'Way' can effect where they end up in the Nevernever.
That being said, would it be right to assume that the stone is more of a utility that senses the 'Ways' as relevant to the user at the moment of use, basically Maggie's affinity for Ways imbued into an item, as opposed to it merely being the collective knowledge of maggie's travels/mapping?