New Twiddle

components.drop-down\.js

import Component from '@glimmer/component';
import { tracked } from '@glimmer/tracking';
import { action } from '@ember/object';

export default class extends Component {
  @tracked isOpen = true;
  @action
  close() {
    this.isOpen = false; 
  }
}

components.menu.internal\.js

import Component from '@glimmer/component';

export default class extends Component {
  constructor(owner, args) {
    super(owner, args);
    this.args.menu.setCloseHandler(args.closeHandler)
  }
}

components.menu\.js

import Component from '@glimmer/component';
import { action } from '@ember/object';

export default class extends Component {
  setCloseHandler(fn) {
    this.closeHandler = fn;
  }
  
  @action
  close() {
    this.closeHandler(); 
  }
}

controllers.application\.js

import Controller from '@ember/controller';

export default class ApplicationController extends Controller {
  appName = 'Ember Twiddle';
}

templates.application\.hbs

<h1>Welcome to {{this.appName}}</h1>
<br>
<br>
{{outlet}}
<br>
<br>

<Menu @isOpen=true >
  sup
</Menu>

templates.components.drop-down\.hbs

{{yield (hash close=(action 'close'))}}

{{#if this.isOpen}}
  Open
{{else}}
  closed
{{/if}}

templates.components.menu.internal\.hbs

{{yield}}

templates.components.menu\.hbs

<DropDown as |dd| >
  <Menu::Internal @menu={{this}} @closeHandler={{action dd.close}}>
    {{yield}}
  </Menu::Internal>
  <button {{action "close"}}>
    Close
  </button>
</DropDown>

twiddle\.json

{
  "version": "0.17.1",
  "EmberENV": {
    "FEATURES": {},
    "_TEMPLATE_ONLY_GLIMMER_COMPONENTS": false,
    "_APPLICATION_TEMPLATE_WRAPPER": true,
    "_JQUERY_INTEGRATION": true
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.5.1/jquery.js",
    "ember": "3.18.1",
    "ember-template-compiler": "3.18.1",
    "ember-testing": "3.18.1"
  },
  "addons": {
    "@glimmer/component": "1.0.0"
  }
}