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?