Can you please add some options to your UI to maximize the space available to code editor textarea? Some ideas on how to do this~

1. Make the layout like Stylish 2.0.7 for Firefox by changing edit.css as follows:

#header { padding: 0; }
#header * { display: inline; }
h1 { display: none; }
h2 { font-size: 1.1em; }
#sections { padding: 0; }
#sections h2 { display: none; }
#sections div { padding: 0; }

...then move options into a #help-popup type overlay.

This would cause Linter errors to obnoxiously show up at the top the second you type an opening brace just as they do now on the left side.

2. If you think the above is too minimalist, you could add a toggle checkbox, similar to what you did with the "New Manage UI layout" one, to switch between the two layouts.

3. The simplest solution may be to add a horizontal resize-grip or maybe change the existing one to work for horizontal and vertical resizing.

It's kind of sad—though certainly not your fault—that I now have to ask you to do this. XUL allowed me to quietly solve past Stylish UI issues (such as AIOS compatibility) on my own.