discourse-custom-wizard/assets/javascripts/wizard/routes/custom-index.js.es6

export default Ember.Route.extend({
  beforeModel() {
    const appModel = this.modelFor('custom');

    if (appModel) {
      if (appModel.completed) {
        this.set('completed', true);
      } else if (appModel.start) {
        this.replaceWith('custom.step', appModel.start);
      }
    }
  },

  setupController(controller) {
    const completed = this.get('completed');
    controller.set('completed', completed);
  }
});