You should be able to just use a website that uses resident keys (such as Microsoft Passwordless login). I don't think the UI is any different, it's just that the key will actually get stored on the device.

Because the first firmware revision lacks the credential management API, there's no way to list the resident keys on the device or to delete individual keys. The only way to delete resident keys AFAIK is to reset the FIDO2 application on the key.