Web Inspector editor is not powerful yet, but I'm working in this direction: https://bugs.webkit.org/show_bug.cgi?id=70182, https://bugs.webkit.org/show_bug.cgi?id=71625, https://bugs.webkit.org/show_bug.cgi?id=70181, https://bugs.webkit.org/show_bug.cgi?id=69986 ...

What bothers you the most?

> So the biggest pain is having to hit refresh (not that big a deal).

You could try http://livereload.com/