Update: Wolfgang Amadeus Mozart
<?php use sjaakp\taggable\TagEditor; ?> ... <?= $form->field($model, 'tags')->widget(TagEditor::class, [ 'clientOptions' => [ 'autocomplete' => [ 'source' => Url::toRoute(['tag/suggest']), ], ] ]) ?> ...
<?php use sjaakp\taggable\TagEditor; ?> ... <?= $form->field($model, 'tags')->widget(TagEditor::class, [ 'clientOptions' => [ 'autocomplete' => [ 'source' => Url::toRoute(['tag/suggest']), ], ] ]) ?> ...