ConstKnobs are plain display values in RoutingModuleConfig, at the paths their ids name.
layers, beforeLayerConfig, the waypoint images, icon mapping, label title and
customTypeface, which take structured, function or MapLibre values or font files, and events
aren't knobs. A displayUnits knob left
unset follows the global config.
Every routing knob with its kind, description, range or options and, where one value holds everywhere, its default. Route-wide knobs come first, then each drawn section type's. It's static data, readable with no map loaded.