SetCustomize::form

public SetCustomize::form(array $form, FormStateInterface $form_state)

public function form(array $form, FormStateInterface $form_state) {
  $form = parent::form($form, $form_state);
  $form['shortcuts'] = array(
    '#tree' => TRUE,
    '#weight' => -20,
  );

  $form['shortcuts']['links'] = array(
    '#type' => 'table',
    '#header' => array(t('Name'), t('Weight'), t('Operations')),
    '#empty' => $this->t('No shortcuts available. <a href=":link">Add a shortcut</a>', array(':link' => $this->url('shortcut.link_add', array('shortcut_set' => $this->entity->id())))),
    '#attributes' => array('id' => 'shortcuts'),
    '#tabledrag' => array(
      array(
        'action' => 'order',
        'relationship' => 'sibling',
        'group' => 'shortcut-weight',
      ),
    ),
  );

  foreach ($this->entity->getShortcuts() as $shortcut) {
    $id = $shortcut->id();
    $url = $shortcut->getUrl();
    if (!$url->access()) {
      continue;
    }
    $form['shortcuts']['links'][$id]['#attributes']['class'][] = 'draggable';
    $form['shortcuts']['links'][$id]['name'] = array(
      '#type' => 'link',
      '#title' => $shortcut->getTitle(),
    ) + $url->toRenderArray();
    unset($form['shortcuts']['links'][$id]['name']['#access_callback']);
    $form['shortcuts']['links'][$id]['#weight'] = $shortcut->getWeight();
    $form['shortcuts']['links'][$id]['weight'] = array(
      '#type' => 'weight',
      '#title' => t('Weight for @title', array('@title' => $shortcut->getTitle())),
      '#title_display' => 'invisible',
      '#default_value' => $shortcut->getWeight(),
      '#attributes' => array('class' => array('shortcut-weight')),
    );

    $links['edit'] = array(
      'title' => t('Edit'),
      'url' => $shortcut->urlInfo(),
    );
    $links['delete'] = array(
      'title' => t('Delete'),
      'url' => $shortcut->urlInfo('delete-form'),
    );
    $form['shortcuts']['links'][$id]['operations'] = array(
      '#type' => 'operations',
      '#links' => $links,
      '#access' => $url->access(),
    );
  }
  return $form;
}