i think, modX is not made for designer, but for coders.
(sorry for english…)
I haven’t yet (beyond the basics) and I find their documentation pretty exasperating at times..
WISIWIG is a bad word, sorry. i mean in the 0.9.2.1 modx version i could have this : (view1) and in the new beta, only code (view2)
<link rel="stylesheet" href="[(site_url)]assets/templates/mytemplate/style.css" type="text/css" media="screen" />