I dont know? Seems like pressing keys is more work than just clicking a mouse button.

Have you tried right clicking on the taskbar shortcut for opening private windows?

Yes, of course I tried, but it is not what I want to do. To really work less you should never take your hands off the keyboard.

true!

You can possibly achieve this with code in an autoconfig.cfg file, but "Ctrl+Shift+N" is taken by Undo Closed Window and thus isn't available and you would have to remove this shortcut key as well.

• /questions/1333526#answer-1409009 Right click menu keyboard shortcut

// autoconfig.cfg must start with a comment line
 try {
  let {classes:Cc, interfaces:Ci, manager:Cm, utils:Cu} = Components;
  const {Services} = Cu.import('resource://gre/modules/Services.jsm');
  function ConfigJS() { Services.obs.addObserver(this, 'chrome-document-global-created', false); }
  ConfigJS.prototype = {
   observe: function (aSubject) { aSubject.addEventListener('DOMContentLoaded', this, {once: true}); },
   handleEvent: function (aEvent) {
    let document = aEvent.originalTarget;
    let window = document.defaultView;
    let location = window.location;
    if (/^(chrome:(?!\/\/(global\/content\/commonDialog|browser\/content\/webext-panels)\.x?html)|about:(?!blank))/i.test(location.href)) {
     if (window._gBrowser) {
      let myKeyChanges = [{id:'key_privatebrowsing',newkey_sc:'N'},{id:'key_undoCloseWindow',newkey_sc:'--'}];
      var i,mK,menuitem;
      for (i=0; mK=myKeyChanges[i]; i++){
       menuitem = window.document.getElementById(mK.id);
       if (menuitem) {
        if (mK.newlabel) menuitem.setAttribute('label', mK.newlabel);
        if (mK.newkey_ac) {
         if (mK.newkey_ac=='--') menuitem.removeAttribute('accesskey');
         else menuitem.setAttribute('accesskey', mK.newkey_ac);
        }
        if (mK.newkey_sc) {
         if (mK.newkey_sc=='--') {
          menuitem.removeAttribute('key');
          menuitem.removeAttribute('modifiers');
         }
         else menuitem.setAttribute('key', mK.newkey_sc);
        }
       }
      }
     }
    }
   }
  };
  if (!Services.appinfo.inSafeMode) { new ConfigJS(); }
 } catch(ex) {};