This allows you to overwrite the shortcode attributes of Helpful. This also overwrites the values defined in the Helpful settings.

/**
 * Can be used to replaced helpful shortcode atts.
 *
 * @param array $atts existing shortcode atts.
 * @return array
 */
function custom_function( $atts ) {
	$defaults['heading'] = 'My custom heading!';
	return $atts;
}

add_filter( 'helpful_shortcode_atts', 'custom_function' );