Select2.js tags, hide dropdown (here Yii2 kartik widget)

select2_tags_dropdown_hide.php

<?php
  echo Select2::widget([
      //...
      'pluginOptions' => [
          'tags' => true,
          'tokenSeparators' => [',', ' '],
          'dropdownCssClass' => 'hide' // <-- hide - Twitter Bootstrap class for hidding dropdown
      ],
      //...
  ])