When adding a Tilemap object to the scene, its configuration allows defining a layer via the Layer index to display setting. Unfortunately the Tilemap Collision Mask does not have this filter, and will instead use all layers on a map to define collision masks. It would be appreciated if the collision mask also offered a layer filter alongside the class filter, allowing you to include or exclude any map layers.
Reason: When designing a map in Tiled, you often use the same tiles for both the playable area as well as foreground / background layers not meant to collide, some tiles containing a collision class. As the collision mask checks the whole map for tiles with that class, background / foreground elements the player is meant to walk through will cause collisions in places where you don’t want them, including invisible collisions from parallax layers that are visually mapped to the camera.