Sorry for the delayed response, but I was temporary offline due to illness.
WixEdit is just the editor. It makes WiX more visual and easier to comprehend and edit. The fancy stuff is really done by WiX, so that is what you should try to master.
Unfortunately there is no tutorial for WixEdit.
About the path environment variable, the WiX tutorial explains it exactly:
So in WixEdit, that means you should create an "environment" element, just within a component. (The same place where files are created.) And for the rest, follow the tutorial.