code: function prefChangeHandler() {
          var prefs = getPreferences();
  
          if (prefs.closeBelow !== menuEntriesShown.closeBelow) {
              if (prefs.closeBelow) {
                  workingSetListCmenu.addMenuItem(closeBelow, "", Menus.AFTER, Commands.FILE_CLOSE);
              } else {
                  workingSetListCmenu.removeMenuItem(closeBelow);
              }
          }
  
          if (prefs.closeOthers !== menuEntriesShown.closeOthers) {
              if (prefs.closeOthers) {
                  workingSetListCmenu.addMenuItem(closeOthers, "", Menus.AFTER, Commands.FILE_CLOSE);
              } else {
                  workingSetListCmenu.removeMenuItem(closeOthers);
              }
          }
  
          if (prefs.closeAbove !== menuEntriesShown.closeAbove) {
              if (prefs.closeAbove) {
                  workingSetListCmenu.addMenuItem(closeAbove, "", Menus.AFTER, Commands.FILE_CLOSE);
              } else {
                  workingSetListCmenu.removeMenuItem(closeAbove);
              }
          }
  
          menuEntriesShown = prefs;
      }
docs: When the preferences changed, add/remove the required menu items