Fields::append

public function append(array $options)
{
	$field = self::$fields[$options['name']];

	if (empty($options['type']) && !empty($field['TYPE']))
	{
		$options['type'] = $field['TYPE'];
	}
	if (empty($options['items']) && !empty($field['ITEMS']))
	{
		$options['items'] = array_map(
			function ($item)
			{
				return [
					'value' => $item['ID'],
					'label' => $item['VALUE'],
				];
			},
			$field['ITEMS']
		);
	}
	if (empty($options['size']) && !empty($field['SIZE']))
	{
		$options['size'] = is_array($field['SIZE']) ? $field['SIZE'] : null;
	}

	$data = $this->getTabletFormattedField([
		'name' => $options['name'],
		'sort' => (count($this->form->getFields()) + 1) * 10,
	] + $options);
	$this->form->merge(['FIELDS' => array_merge(
		$this->form->getFields(),
		[$data]
	)]);
}