New Twiddle

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  actions: {
    test() {
      this.set('message','successfully added');
    }
  }
});

templates.application.hbs

<button onclick={{action "test" model.id}}>Test</button>

{{#if message}}
  {{#modal-dialog
    onClose=(action (mut isShowingBasic) false)
  }}
    {{message}}
  {{/modal-dialog}}
{{/if}}

twiddle.json

{
  "version": "0.15.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.4.3",
    "ember-template-compiler": "3.4.3",
    "ember-testing": "3.4.3"
  },
  "addons": {
    "ember-data": "3.4.2",
    "ember-modal-dialog": "3.0.0-beta.0"
  }
}