The following code can be used as a phpblock. It shows a nice and small notepad using localStorage, which is local to the Browser. [not suitable for shared machines !]
Text Formatted Code
<div>
<textarea id="gl_NotePad" placeholder="Type here, see it persist again …" rows="5" style="width:100%;"></textarea>
<script>
var glNote = document.getElementById('gl_NotePad');
glNote.onchange = function(){localStorage.setItem("geeklog",glNote.value);}
glNote.value = localStorage.getItem("geeklog");
</script>
</div>
Set it to display just below the user functions. Disable anonymous access.