add_filter( 'genesis_attr_site-inner', 'sk_attributes_site_inner' );
/**
 * Add attributes for site-inner element.
 *
 * @since 2.0.0
 *
 * @param array $attributes Existing attributes.
 *
 * @return array Amended attributes.
 */
function sk_attributes_site_inner( $attributes ) {

    $attributes['role']     = 'main';
    $attributes['itemprop'] = 'mainContentOfPage';
    $attributes['id'] = 'genwpacc-genesis-content';

    return $attributes;

}