code: function optOnIconMouseDownListener (e) { // outlineIcons.src.icon_opton  needed?
      var target = thisOutline.targetOf(e)
      var p = target.parentNode
      termWidget.replaceIcon(p.parentNode,
        outlineIcons.termWidgets.optOn,
        outlineIcons.termWidgets.optOff, optOffIconMouseDownListener)
      p.parentNode.parentNode.removeAttribute('optional')
    }
docs: These woulkd be simpler using closer variables below