Filter wp_nav_menu_objects. It will contain the sorted list of nav menu items to render. Have a look at wp_setup_nav_menu_item for some properties you can use.

Here's a quick (untested) example.

add_filter( 'wp_nav_menu_objects', function( array $items, array $args ) {

    if ( 'someThemeLocation' !== $args->theme_location ) {
        return $items;
    }

    return array_filter( $items, function( $item ) {
        return '/user-specific-thingy' === $item->url 
            && ! is_user_logged_in();
    } );

}, 10, 2 );

Filter wp_nav_menu_objects. It will contain the sorted list of nav menu items to render. Have a look at wp_setup_nav_menu_item for some properties you can use.

Here's a quick (untested) example.

add_filter( 'wp_nav_menu_objects', function( array $items, object $args ) {

    if ( 'someThemeLocation' !== $args->theme_location ) {
        return $items;
    }

    return array_filter( $items, function( $item ) {
        return '/user-specific-thingy' === $item->url 
            && ! is_user_logged_in();
    } );

}, 10, 2 );

Filter wp_nav_menu_objects. It will contain the sorted list of nav menu items to render. Have a look at wp_setup_nav_menu_item for some properties you can use.

Here's a quick (untested) example.

add_filter('wp_nav_menu_objects', 'wpse233667_nav_menu_objects', 10, 2);
function wpse233667_nav_menu_objects($items, $args)
 {
  if ('someThemeLocation' !== $args->theme_location) {
    return $items;
  }

  $out = [];
  foreach ($items as $item) {
    if ('/user-specific-thingy' === $item->url && !is_user_logged_in()) {
      continue;
    }
    $out[] = $item;
  }

  return $out;
}

Filter wp_nav_menu_objects. It will contain the sorted list of nav menu items to render. Have a look at wp_setup_nav_menu_item for some properties you can use.

Here's a quick (untested) example.

add_filter( 'wp_nav_menu_objects', function( array $items, array $args ) { 

    if ( 'someThemeLocation' !== $args->theme_location ) {
        return $items;
    }

    return array_filter( $items, function( $item ) {
        return '/user-specific-thingy' === $item->url 
            && ! is_user_logged_in();
    } );

}, 10, 2 );