Wie erstellt man keyboard shortcuts ?

(function() {

    if (!window.gBrowser){
        return;
    }
    
    // ...  
    // Key-Event:  
    // ...
    window.addEventListener("keydown", event => {
            //console.log("Key: " + event.code + " | " + event.ctrlKey);
                        
            if( event.code == "ArrowLeft" && event.ctrlKey) 
            {
                gBrowser.tabContainer.advanceSelectedTab( -1, true );
            }
            else if(event.code == "ArrowRight" && event.ctrlKey) 
            {
                gBrowser.tabContainer.advanceSelectedTab( 1, true );
            }
    });

})();

// ==UserScript==
// key.CloseAllTabs_aborix.uc.js
// https://www.camp-firefox.de/forum/viewtopic.php?p=1099118#p1099118
// ==/UserScript== 

(function() {
   setTimeout(function() {
  var browser_chrome = 'chrome://browser/content/browser.xhtml';

  if (location != browser_chrome)
    return;
 
  let key = document.createXULElement('key');
  key.id = 'key_closeAllTabs';
  key.setAttribute('key', 'W');
  // key.setAttribute('keycode', 'VK_F1')
  key.setAttribute('modifiers', 'alt');
  key.setAttribute('oncommand',
    'gBrowser.removeAllTabsBut(gBrowser.selectedTab); gBrowser.removeTab(gBrowser.selectedTab);');
  document.getElementById('mainKeyset').appendChild(key);
   }, 6000);
})();