\defaultfontfeatures[MonaspaceXenon-ExtraLight]
{
  Extension=.otf,
  UprightFont=MonaspaceXenon-ExtraLight,
  ItalicFont=MonaspaceXenon-ExtraLightItalic,
  BoldFont=MonaspaceXenon-Regular,
  BoldItalicFont=MonaspaceXenon-Italic
}