Bookmarklet to edit current URL
Just change window.location, e.g.
window.location=window.location.toString().replace(/^http:\/\/www\./,'https://admin.')
For example you could replace a part of the string using the replace method with a regular expression.
javascript:location = location.href.replace(/http:/g, "https:" ) The above will assign the new string value to the location and trigger the page reload.
This one will change the site name
javascript:(function() {document.title=prompt("Enter Page Title");})();