in your script and then look at HTML/CSS/Script directly in QlikView Desktop (skipping the Server steps). No support for breakpoints though...
But due to lack of breakpoints and stepping, I also run all my development from a server.
To automate the process, I use grunt.js (http://gruntjs.com/) to simplify development of extensions. Change the code, run grunt and then test. Some work to set up the environment though but if you are into heavy extension development then its well invested time.