ModerationStateTransitionForm::form

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

public function form(array $form, FormStateInterface $form_state) {
  $form = parent::form($form, $form_state);

  /* @var \Drupal\content_moderation\ModerationStateTransitionInterface $moderation_state_transition */
  $moderation_state_transition = $this->entity;
  $form['label'] = [
    '#type' => 'textfield',
    '#title' => $this->t('Label'),
    '#maxlength' => 255,
    '#default_value' => $moderation_state_transition->label(),
    '#description' => $this->t('Label for the Moderation state transition.'),
    '#required' => TRUE,
  ];

  $form['id'] = [
    '#type' => 'machine_name',
    '#default_value' => $moderation_state_transition->id(),
    '#machine_name' => [
      'exists' => '\Drupal\content_moderation\Entity\ModerationStateTransition::load',
    ],
    '#disabled' => !$moderation_state_transition->isNew(),
  ];

  $options = [];
  foreach ($this->entityTypeManager->getStorage('moderation_state')
    ->loadMultiple() as $moderation_state) {
    $options[$moderation_state->id()] = $moderation_state->label();
  }

  $form['container'] = [
    '#type' => 'container',
    '#attributes' => [
      'class' => ['container-inline'],
    ],
  ];

  $form['container']['stateFrom'] = [
    '#type' => 'select',
    '#title' => $this->t('Transition from'),
    '#options' => $options,
    '#required' => TRUE,
    '#empty_option' => $this->t('-- Select --'),
    '#default_value' => $moderation_state_transition->getFromState(),
  ];

  $form['container']['stateTo'] = [
    '#type' => 'select',
    '#options' => $options,
    '#required' => TRUE,
    '#title' => $this->t('Transition to'),
    '#empty_option' => $this->t('-- Select --'),
    '#default_value' => $moderation_state_transition->getToState(),
  ];

  // Make sure there's always at least a wide enough delta on weight to cover
  // the current value or the total number of transitions. That way we
  // never end up forcing a transition to change its weight needlessly.
  $num_transitions = $this->queryFactory->get('moderation_state_transition')
    ->count()
    ->execute();
  $delta = max(abs($moderation_state_transition->getWeight()), $num_transitions);

  $form['weight'] = [
    '#type' => 'weight',
    '#delta' => $delta,
    '#options' => $options,
    '#title' => $this->t('Weight'),
    '#default_value' => $moderation_state_transition->getWeight(),
    '#description' => $this->t('Orders the transitions in moderation forms and the administrative listing. Heavier items will sink and the lighter items will be positioned nearer the top.'),
  ];

  return $form;
}