What is the point of adding new layers in project settings, and how to use them?

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:bust_in_silhouette: Asked By Bernard Cloutier

I’ve noticed that you can add new layers beyond the base 20 ones, whether for physics or rendering.

I fail to understand how these can work with the bit masks, and they don’t show up in the editor interface. To use the 21st layer I’ve added, I tried doing set_layer_mask_bit(1 << 20, true) on a MeshInstance and set_cull_mask_bit(1 << 20, true) on my camera, but to no effect.

What is the purpose of these custom layers and how do you use them?