New Twiddle

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  
  conditions: [],
  
  actions: {
    addCondition(e) {
      this.conditions.pushObject(e.target.value);
    }
  }
});

templates.application.hbs

<ul>
  {{#each conditions as |cond|}}
    <li>{{cond}}</li>
  {{/each}}
</ul>

<select onchange={{action "addCondition"}} value={{conditionType}}>
  <option value="" disabled hidden selected="selected">
    Add condition
  </option>

  <option value="1" selected={{eq "1" conditionType}}>
    Condition 1
  </option>
  <option value="2" selected={{eq "2" conditionType}}>
    Condition 2
  </option>
</select>

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-truth-helpers": "2.1.0"
  }
}