Drupal 8: Table drag

entityListBuilder.php

<?php  
public function buildForm(array $form, FormStateInterface $form_state) {
    $form = parent::buildForm($form, $form_state);
    if ($this->entities) {
      /** @var \Drupal\commerce_promotion\Entity\Promotion $promotion */
      foreach ($this->entities as $promotion) {
        $form['promotions'][$promotion->id()]['name'] = [
          'name' => $form['promotions'][$promotion->id()]['name'],
        ];
        $has_parent = FALSE;
        $parent_id = 0;
        if ($promotion->hasField('parent') && $promotion->parent->target_id) {
          $has_parent = TRUE;
          $parent_id = $promotion->parent->target_id;
        }
        $form['promotions'][$promotion->id()]['name']['parent'] = [
          '#type' => 'hidden',
          '#default_value' => $parent_id,
          '#attributes' => [
            'class' => ['promotion-parent'],
          ],
        ];
        $form['promotions'][$promotion->id()]['name']['depth'] = [
          '#type' => 'hidden',
          '#default_value' => $has_parent ? 1 : 0,
          '#attributes' => [
            'class' => ['promotion-depth'],
          ],
        ];
      $form['promotions'][$promotion->id()]['name']['weight'] = [
        '#type' => 'weight',
        '#title' => $this->t('Weight for @title', ['@title' => $entity->label()]),
        '#title_display' => 'invisible',
        '#default_value' => $entity->getWeight(),
        '#attributes' => ['class' => ['weight']],
      ];
        $indentation = [];
        if ($has_parent) {
          $indentation = [
            '#theme' => 'indentation',
            '#size' => 1,
          ];
        }

        $form['promotions'][$promotion->id()]['name']['#prefix'] = !empty($indentation) ? $this->renderer->render($indentation) : '';
        $form['promotions'][$promotion->id()]['name']['pid'] = [
          '#type' => 'hidden',
          '#value' => $promotion->id(),
          '#attributes' => [
            'class' => ['promotion-id'],
          ],
        ];
      }
    }
    $form['promotions']['#tabledrag'][] = [
      'action' => 'order',
      'relationship' => 'sibling',
      'group' => 'weight',
    ];
    $form['promotions']['#tabledrag'][] = [
      'action' => 'match',
      'relationship' => 'parent',
      'group' => 'promotion-parent',
      'subgroup' => 'promotion-parent',
      'source' => 'promotion-id',
      'hidden' => FALSE,
    ];
    $form['promotions']['#tabledrag'][] = [
      'action' => 'depth',
      'relationship' => 'group',
      'group' => 'promotion-depth',
      'hidden' => FALSE,
    ];

    return $form;
  }