MapObjectLayer

Puts the map objects of content into an independent collection linked to layerId, instead of the default collection of the map.

The layer picks the place of the objects in the render order; changing layerId moves them to another layer. MapKit links one collection to a layer id for the lifetime of the map and cannot unlink it, so the collection is created once per id and reused: leaving the composition empties it and entering it again fills the same collection.