Panels - CSS viewer

how to insert css rules

At the top of the "css viewer" panel there is a dropdown with the "conditional group rules" present in the current stylesheet. Here you can add, select and delete "group rules" (at the moment you can only enter media queries. Both media queries and support rules will appear in the list).
Click in the panes in the image below for more information
tilepieces documentation - insert-css-rules

New media query form

tilepieces documentation - css-new-media-query-form