It would be really nice if you could assign a batch file to the test button and not just a script.

When tesking multiplayer I often want to open a server and client and use a batch file to do this. But leaving the SED enviroment everytime I want to run, and having to keep an explorer window open is a real pain.

You could start other engine instances through the exec() function at the begin of your script. I haven't tried it, but it should do the same tasks as a batch file.