Add widget area after .menu in Genesis Primary Nav. Source: https://gist.github.com/NicktheGeek/4503511

functions.php

//* Register widget area
genesis_register_sidebar( array(
  'id'          => 'nav-right',
	'name'        => __( 'Nav Right', 'genesis-sample' ),
	'description' => __( 'This is after .menu in .nav-primary', 'genesis-sample' ),
) );


// Adds widget area after .menu in .nav-primary
add_filter( 'genesis_do_nav', 'sk_do_nav_widget', 10, 2 );
function sk_do_nav_widget( $nav_output, $nav ){
	ob_start();
	genesis_widget_area( 'nav-right', array(
		'before' => '<div class="nav-right widget-area">',
	) );
	$widget_area = ob_get_clean();

	return str_replace( $nav, $nav . $widget_area, $nav_output );
}