Show HN: “Digital Scrap Paper” – simple, private in-browser note taking (github.com)

  data:text/html,<h3 contenteditable oninput="document.title=this.innerHTML">untitled</h3><div contenteditable>note</div>

Put this in your address bar or bookmark it. Same functionality as yours, but you can save note's content with Ctrl + S since it's a div tag instead of textarea.