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components.my-component\.js

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

export default class extends Component {
  
  @tracked items

	constructor() {
    super(...arguments);
    this.items = [1,2,3];
  }
  
  get reversedItems() {
    return ([...this.items]).reverse();  
  } 
  
  @action addRow() {
    this.items = [...this.items, this.items.length + 1];
  }
  
}

controllers.application\.js

import Controller from '@ember/controller';

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

styles.app\.css

body {
  margin: 12px 16px;
  font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
  font-size: 12pt;
}

.scrollable-container {
  border: 10px solid red;
  height: 500px;
  overflow: auto;
  
  display: flex;
  flex-direction: column-reverse;
}

templates.application\.hbs

<MyComponent />

templates.components.my-component\.hbs

<div class='scrollable-container'>
  {{#each this.reversedItems as |item|}}
    <p>Some item {{item}}</p>
  {{/each}}
</div>

<button {{on "click" this.addRow}}>Add row</button>

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"
  }
}