New Twiddle

components.my-component\.js

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

    class ReactivePart {
        constructor(placeholder) {
            this.value = placeholder.replace('{{', '').replace('}}','');
          	this.placeholder = placeholder;
        }
      	get isEditable() {
        	return this.placeholder.startsWith('{{');
        }
        @tracked value;
      	toString() {
        	return this.isEditable ? `{{${this.value}}}` : this.value;
        }
    }

export default class extends Component {
  
  
   weakParts = new WeakMap();
        get parts() {
            const substitutions = this.args.template;
            if (!this.weakParts.has(substitutions)) {
                this.weakParts.set(
                    substitutions, 
                    substitutions.map((placeholder) => new ReactivePart(placeholder))
                )
            }

            return this.weakParts.get(substitutions);
        }

   get newTemplate() {
   			return this.parts.map(e=>e.value && e.toString()).join(' ');
   }

}

controllers.application\.js

import Controller from '@ember/controller';

export default class ApplicationController extends Controller {
  tpl = "hero {{1}} bora {{2}} herobora {{1}}";
	get template() {
  	return this.tpl.split(' ');
  }
}

templates.application\.hbs

<select>
<MyComponent @template={{this.template}} />

templates.components.my-component\.hbs

<br>
{{@template}}
<br><br><br>
{{#each this.parts as |part|}}
	{{#if part.isEditable}}
  		<Input @value={{part.value}} />
  {{else}}
  	{{part.value}}
   {{/if}}
{{/each}}
<br><br><br>
{{this.newTemplate}}

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"
  }
}