Porto

A short land leg, which is the case where a straight line stops being good enough. Give a leg a land transport mode and its route can be snapped to real geometry rather than guessed.

The reason it is not stored as a chip

A snapped route is a polyline — tens of thousands of coordinate pairs. It lives in the document's metadata but is deliberately hidden from the editor, because a metadata chip stringifies its value on the main thread and that one would lock the tab. It is drawn by the map and edited by the route panel, never typed.