How are you supposed to use XRPackageMetadataStore.AssignLoader?

I don't understand the use of this, because Unity isn't letting me use it. It exists to allow you to swap in multiple different XRManagerSettings assets, but you can't make multiple XRManagerSettingsAssets. If you put one in your assets folder, Unity automatically turns it into an XRGeneralSettingsPerBuildTarget asset, so there's never any way for you to have an XRManagerSettings assets that you can plug into this function. Which means, as far as I can tell, there's no way for you to change XR settings via a script.

Additionally, I have no clue how Im supposed to know what "loaderTypeName" is supposed to be. Im trying to do this for Oculus OVR and OpenXR but I've found no reference to a "loaderTypeName" for those packages anywhere.

If you want to programmatically add/remove loaders or change loader order you can look at this documentation here: End-user documentation | XR Plugin Management | 4.2.1 (