Custom activity status update VBO .module file

civicrm_customs.module

function civicrm_customs_action_info() {
  return array(
    'civicrm_customs_update_activity_status_action' => array(
      'type' => 'civicrm_activity',
      'label' => t('Update Activity Status'),
      'behavior' => array('views_property'),
      'configurable' => FALSE,
      'vbo_configurable' => TRUE,
      'triggers' => array('any'),
      'pass rows' => TRUE,
    ),
  );
}

// The function name must be [action_name] + '_form'.
function civicrm_customs_update_activity_status_action_form($settings, &$form_state) {
  civicrm_initialize();

  $activity_status_options_result = civicrm_api3('Activity', 'getoptions', [
    'field' => "activity_status_id",
  ]);

  $form = array();
  $form['activity_status'] = array(
    '#type' => 'select',
    '#title' => t('Activity Status'),
    '#options' => $activity_status_options_result['values'],
    '#required' => TRUE,
    '#default_value' => "1",
  );
  return $form;
}

// The function name must be [action_name] + '_submit'.
function civicrm_customs_update_activity_status_action_submit($form, $form_state) {
  $return = array();
  $return['activity_status'] = $form_state['values']['activity_status'];
  return $return; //Note, return value here must be an array.
}

function civicrm_customs_update_activity_status_action(&$entity, $context) {
  $result = civicrm_api3('Activity', 'create', [
    'id' => $entity->id,
    'activity_status_id' => $context['activity_status'],
  ]);
}