New Twiddle

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  
  session: {
    backend_pl_fields: [
    ],
  },
  
  actions: {
    addField() {
      this.get('session.backend_pl_fields').pushObject({field_name: Math.random()});
    },
    removeField() {
      this.get('session.backend_pl_fields').shiftObject();
    }
  }
});

templates.application.hbs

<button {{action "addField"}}>Add Field</button><button {{action "removeField"}}>Remove Field</button>
{{#each session.backend_pl_fields as |field index|}}
   <label class="fields-label">Field {{index}}</label>
      <button class="round-small-tertiary-button" {{action "deleteField" index}}>
      </button>
      <div id="field-{{index}}">
        <fieldset class="input">
          <label class="required" for="field_{{index}}_name">Field Name</label>
          <input value=field.field_name id="field_{{index}}_name" type="text" required="true" />
        </fieldset>
        <fieldset class="input">
          <label class="required" for="field_{{index}}_type">Field Type</label>
          <input value=field.field_type id="field_{{index}}_type" type="text" required="true" />
        </fieldset>
        <fieldset class="doc">
          <label for="field_{{index}}_doc">Doc</label>
          <textarea value=field.doc id="field_{{index}}_doc" cols="80" rows="6"></textarea>
        </fieldset>
      </div>
    {{/each}}

twiddle.json

{
  "version": "0.12.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.12.0",
    "ember-template-compiler": "2.12.0",
    "ember-testing": "2.12.0"
  },
  "addons": {
    "ember-data": "2.12.1"
  }
}