Drupal block display menu siblings and children, with config

MenuSiblings.php

<?php

namespace Drupal\MY_MODULE_NAME\Plugin\Block;

use Drupal\Core\Block\BlockBase;
use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
use Symfony\Component\DependencyInjection\ContainerInterface;
use Drupal\Core\Form\FormStateInterface;
use Drupal\Core\Cache\Cache;

use Drupal\Core\Menu\MenuLinkTree;
use Drupal\Core\Menu\MenuTreeParameters;
use Drupal\Core\Render\Markup;
use Drupal\Core\Url;
use Drupal\Core\Link;

/**
 * Provides a 'Menu Siblings' block.
 *
 * @Block(
 *  id = "menu_siblings",
 *  admin_label = @Translation("Menu Siblings"),
 * )
 */
class MenuSiblings extends BlockBase implements ContainerFactoryPluginInterface {

  /**
   * The entity type manager service.
   *
   * @var \Drupal\Core\Menu\MenuLinkTree
   */
  protected $menuTree;


  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
    $instance = new static($configuration, $plugin_id, $plugin_definition);
    $instance->menuTree = $container->get('menu.link_tree');
    return $instance;
  }


  /**
   * {@inheritdoc}
   */
  public function blockForm($form, FormStateInterface $form_state) {
    $form = parent::blockForm($form, $form_state);

    $config = $this->getConfiguration();

    $form['display_children'] = [
      '#title' => $this->t('Display children ?'),
      '#type' => 'checkbox',
      '#default_value' => $config['display_children'] ?? FALSE,
    ];

    return $form;
  }
  /**
   * {@inheritdoc}
   */
  public function blockSubmit($form, FormStateInterface $form_state) {
    parent::blockSubmit($form, $form_state);
    $values = $form_state->getValues();
    $this->configuration['display_children'] = $values['display_children'];
  }


  /**
   * {@inheritdoc}
   */
  public function build() {
    $config = $this->getConfiguration();
    $depth = (!empty($config['display_children']) && $config['display_children']) ? 2 : 1;
    $menu = $this->getMainMenu($depth);
    if (!empty($menu)) {
      // Override theme suggestions
      $menu['#theme'] = 'menu__arrow';

      return [
        'menu' => $menu,
      ];
    }
  }


  private function getMainMenu($depth = 1) {

    // This one will give us the active trail in *reverse order*.
    // Our current active link always will be the first array element.
    $parameters   = $this->menuTree->getCurrentRouteMenuTreeParameters('main');
    $active_trail = array_keys($parameters->activeTrail);

    // But actually we need its parent.
    // Except for <front>. Which has no parent.
    $parent_link_id = isset($active_trail[1]) ? $active_trail[1] : $active_trail[0];

    // Having the parent now we set it as starting point to build our custom
    // tree.
    $parameters->onlyEnabledLinks();
    $parameters->setRoot($parent_link_id);
    $parameters->setMaxDepth($depth);
    $parameters->excludeRoot();
    $tree = $this->menuTree->load('main', $parameters);

    // Sort by weight
    $manipulators = [
      ['callable' => 'menu.default_tree_manipulators:generateIndexAndSort']
    ];
    $tree = $this->menuTree->transform($tree, $manipulators);

    // Finally, build a renderable array and enable proper caching.
    return $this->menuTree->build($tree);
  }


  public function getCacheTags() {
    return Cache::mergeTags(parent::getCacheTags(), []);
  }

  public function getCacheContexts() {
    return Cache::mergeContexts(parent::getCacheContexts(), [
      'languages:language_content',
      'route',
      'url.query_args'
    ]);
  }

}