Use it to position custom layers relative to standard map layers, for example below labels.
mapStyleLayerIDs maps each name to its style layer ID.
// Add a custom layer below the POIs
const beforeLayer: MapStyleLayerID = 'poi';
map.mapLibreMap.addLayer({
id: 'my-custom-layer',
type: 'fill',
source: 'my-source'
}, mapStyleLayerIDs[beforeLayer]);
// Position geometry below all labels
const geometryConfig = { beforeLayerConfig: 'lowestLabel' };
mapStyleLayerIDs for the complete list of available layer IDs
The name of a known layer of the TomTom map style: a key of mapStyleLayerIDs.