By Sara Froehlich

As for changes to the panel itself, you can ctrl + click (Mac) or right +click on a PC (I have a two-button mouse and right-clicking doesn’t work for me on the Mac) on a graphic style thumbnail in the panel to see a preview of how the style would look applied to the selected object. You can also view the thumbnail previews in the panel as applied to a square (the default) or text (the letter T).
Another new feature is the ability to layer Graphic Styles.

Opt/Alt + click on any effect to add it to the existing style.