controller.js

watchTags: Ember.on('init', Ember.observer('tagList', function () {
    var tagList = this.get('tagList');
    var justTagList = [];
    tagList.forEach(function (item) {
      justTagList.pushObject(item.get('crmTag'));
    });
    this.set('selectedTags', justTagList);
    this.set('initialTags', justTagList);
})),

actions: {
     // create a brand new tag since this wasn't detected in our list
    createTag (select, e) {
      var self = this;
      var store = this.get('targetObject.store');
      if (e.keyCode === 13 &&
        select.isOpen &&
        !select.highlighted &&
        !Ember.isBlank(select.searchText)) {
          let term = select.searchText;
          let isExisting = this.get('tags').findBy('name', term);

          // to not call submit
          e.preventDefault();
          // to avoid calling this twice
          e.stopPropagation();

          if (!isExisting) {
            let newTag = store.createRecord('crm-tag', {name: term});

            newTag.save().then(() => {
              //register new tag in the widget
              let tags = self.get('tags').toArray();
              tags.pushObject(newTag);
              self.set('tags', tags);
              var selectedTags = self.get('selectedTags');
              selectedTags.pushObject(newTag);
              select.actions.close(e);
            }, (reason) => {
              self.validationReport(newTag);
            });
          }
        }
    }
}