It took me awhile to figure this out, but if you double click on the element styling you want to add additional CSS to (for example, the right column shows #content p has "color:#bbb;", double click on the "color:#bbb" part), add semicolons and the new style after the old one. (with the example the single line textbox should have "color:#bbb;padding:2em;") It'll correctly parse and add the new styling.