I couldn't use the search. So I appologize if someone already suggested this.
It would be nice to have the list of templace pages on the right hand side of the theme editor page to be collapsible in order to make the editor window wider.
It would be similar to the navigation links which pop out on the left hand side of the window when you mouse over them.
You could have it be 33px wide which would add 150+ pixels to the width of the editor window.