Feedback Unity XR SDK in Editor. Native XRInputSystem, XRMeshSubsystem, XRDisplaySubsystem in the Editor.

This thread is a response to this one (called "XR SDK missing documentation"), but with SEO optimizations for future visitors:
https://forum.unity.com/threads/xr-sdk-missing-documentation.974202/

Recently, I spent several days trying to understand why my custom XRInputSystem doesn't work in the Editor. It turns out, you have to add the xreditorsubsystem tag to the manifest.json file of your package.

My other discovery that I didn't find the documentation for: when using AR Foundation, native XRInputSystem only works with Unity >= 2020.1 and AR Foundation >= 4.0.
It's possible to read values supplied by the native XRInputSystem in Unity 2019.4 with the help of InputTracking.GetNodeStates(), but in my experience, only the XRNode.HardwareTracker node is available.