This filter adds the ability to include more data into the CSS being generated. This is put at the bottom of the file and contains the saved data array. Any new data keys added require the use of either this filter or one of the inline CSS filters to actually write the values.

function my_custom_builder( $custom, $data, $class ) {
	if ( isset( $data['my-custom-key'] ) && !empty( $data['my-custom-key'] )  )
		$custom	= $class.' div.awesome {color: '. $data['my-custom-key'].' }';
	return $custom;
add_filter ( 'gppro_css_builder', 'my_custom_builder', 10, 3 );