Добавить атрибут к созданному тегу select2

$(".select_multiple").select2({
    tags: true,
  createTag: function (params) {
    if (!Number.isInteger(parseInt(params.term))) {
      return null;
    }
    return {
      id: params.term,
      text: params.term,
      newOption: true,
      type: "text_type"
    }
  }
})
$('.select_multiple').on('select2:select', function (e) {
    console.log($(e.params.data.element).data('type'));
});

.select_multiple {
  width: 500px;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<link href="https://cdn.jsdelivr.net/npm/[email protected]/dist/css/select2.min.css" rel="stylesheet" />
<script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/js/select2.min.js"></script>
<select class="select_multiple" multiple="multiple">
    <option data-type="1">Date</option>
</select>