shared-in-element

controllers.application\.js

import Controller from '@ember/controller';

export default class ApplicationController extends Controller {
}

demo.component\.js

import Component from '@ember/component';

export default Component.extend({
  didInsertElement() {
    this._super(...arguments);
    this.set('customMessagesContainer', this.element.querySelector('.custom-messages-container'));
  }
});

demo.template\.hbs

{{the-form-field}}
{{the-form-field}}
{{the-form-field}}

{{the-form-field customMessagesContainer=customMessagesContainer}}
{{the-form-field customMessagesContainer=customMessagesContainer}}
{{the-form-field customMessagesContainer=customMessagesContainer}}

<div class="custom-messages-container"></div>

templates.application\.hbs

{{demo}}

the-form-field.component\.js

import Component from '@ember/component';

export default Component.extend({
  customMessagesContainer: null
});

the-form-field.template\.hbs

<div>THE-FORM-FIELD</div>

{{#if customMessagesContainer}}
  {{#-in-element customMessagesContainer}}
    <ul>
      <li>err1 {{this.elementId}}</li>
      <li>err2</li>
      <li>err3</li>
    </ul>
  {{/-in-element}}
{{else}}
  <ul>
    <li>err1 {{this.elementId}}</li>
    <li>err2</li>
    <li>err3</li>
  </ul>
{{/if}}

twiddle\.json

{
  "version": "0.17.0",
  "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/3.3.1/jquery.js",
    "ember": "3.17.0",
    "ember-template-compiler": "3.17.0",
    "ember-testing": "3.17.0"
  },
  "addons": {
    "@glimmer/component": "1.0.0"
  }
}