Is there any way to add custom CSS classes in the CSS Editor?
The CSS Editor menu
Definitely. The ability to add custom classes and allow direct editing of the stylesheet was one of the reasons we designed the CSS Editor. To add these simply bring up the CSS Editor and use the menu on the upper left to navigate to the advanced section. Here you are presented with a textbox that contains all of the css associated with this CSS Editor. You can add new CSS selectors or modify current ones.