Approach1

components.alerts\.js

import Component from '@glimmer/component';

export default class Alerts extends Component {
}

components.filters\.js

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

export default class Filters extends Component {
  init() {
    this.args.initializeFilters(1);
  }
  
  @action
  increaseFilter() {
    this.args.increaseFilter();
  }
}

controllers.application\.js

import Controller from '@ember/controller';

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

controllers.index\.js

import Controller from '@ember/controller';
import { tracked } from '@glimmer/tracking';

export default Ember.Controller.extend({
  @tracked filterValue: null,
  
  actions: {
  	initializeFilters(filterValue) {
  		this.filterValue = filterValue;
		},

    increaseFilter() {
      this.filterValue++;
    }
  }
});

controllers.jymbii\.js

import Controller from '@ember/controller';
import { tracked } from '@glimmer/tracking';

export default Ember.Controller.extend({
  @tracked filterValue: null,
  
  actions: {
  	initializeFilters(filterValue) {
  		this.filterValue = filterValue;
		},

    increaseFilter() {
      this.filterValue++;
    }
  }
});

models.application\.js

import Model from 'ember-data/model';
/*
import attr from 'ember-data/attr';
import { belongsTo, hasMany } from 'ember-data/relationships';
*/

export default class extends Model {
}

models.index\.js

import Model from 'ember-data/model';
/*
import attr from 'ember-data/attr';
import { belongsTo, hasMany } from 'ember-data/relationships';
*/

export default class Index extends Model {
}

models.jymbii\.js

import Model from 'ember-data/model';
/*
import attr from 'ember-data/attr';
import { belongsTo, hasMany } from 'ember-data/relationships';
*/

export default class extends Model {
}

router\.js

import EmberRouter from '@ember/routing/router';
import config from './config/environment';

const Router = EmberRouter.extend({
  location: 'none',
  rootURL: config.rootURL
});

Router.map(function() {
  this.route('jymbii');
});

export default Router;

routes.index\.js

import Route from '@ember/routing/route';

export default Route.extend({
});

routes.jymbii\.js

import Route from '@ember/routing/route';

export default Route.extend({
});

templates.application\.hbs

<div style="outline: 1px solid black;">
  <h1>Approach 1 - Ember; Data Down, Actions Up</h1>
  {{outlet}}
</div>

templates.components.alerts\.hbs

<div style="outline: 1px solid black; width: 80%; margin: 20px; padding: 10px;">
    <h3>
        Alerts component
    </h3>

    <div>
      Data passed down into the component reflects here
    </div>
  
    <div>
      Current Filter Value = @filterValue = {{@filterValue}}
    </div>
</div>

templates.components.filters\.hbs

<div style="outline: 1px solid black; width: 80%; margin: 20px; padding: 10px">
    <h3>
        Filters component
    </h3>

    <div>
      Actions triggered here are bubbled up to the 'experience' route
    </div>
  
    <div> init() { </div>
    <div> &nbsp; &nbsp; this.args.initializeFilters(1); </div>
    <div> } </div>

  	<div> increaseFilter() { </div>
    <div> &nbsp; &nbsp; this.args.increaseFilter(); </div>
  	<div> } </div>

    <div>
      <button onclick={{action "increaseFilter"}}> Add </button>
    </div>
</div>

templates.index\.hbs

<div style="outline: 1px solid black; width: 80%; margin: 20px;padding: 10px;">
  <h2>
    Index route loaded
  </h2>
  
  <div>
  	<p> Route contains all the data/state </p>
    <p> Actions bubbled up from components are handled here </p>
  </div>
  
  <h4> Index Controller </h4>
  <div> @tracked filterValue: null </div>
  <div> initializeFilters(filterValue) { this.filterValue = filterValue; } </div>
  <div> increaseFilter() { this.filterValue++; } </div>

	<h4> Index Template </h4>
  <div> Filters </div>
  <div> &nbsp; &nbsp; @increaseFilter=action 'increaseFilter' </div>
  <div> &nbsp; &nbsp; @initializeFilters=action 'initializeFilters' </div>

  <Filters
    @increaseFilter={{action 'increaseFilter'}}
    @initializeFilters={{action 'initializeFilters'}}
  />
  
  <div> Alerts </div>
  <div> &nbsp; &nbsp; @filterValue=this.filterValue </div>
  <Alerts
    @filterValue={{this.filterValue}}
  />
</div>

templates.jymbii\.hbs

<div style="outline: 1px solid black; width: 80%; margin: 20px;padding: 10px;">
  <h2>
    JYMBII route loaded
  </h2>
  
  <div>
  	<p> Route contains all the data/state </p>
    <p> Actions bubbled up from components are handled here </p>
  </div>
  
  <h4> Index Controller </h4>
  <div> @tracked filterValue: null </div>
  <div> initializeFilters(filterValue) { this.filterValue = filterValue; } </div>
  <div> increaseFilter() { this.filterValue++; } </div>

	<h4> Index Template </h4>
  <div> Filters </div>
  <div> &nbsp; &nbsp; @increaseFilter=action 'increaseFilter' </div>
  <div> &nbsp; &nbsp; @initializeFilters=action 'initializeFilters' </div>

  <Filters
    @increaseFilter={{action 'increaseFilter'}}
    @initializeFilters={{action 'initializeFilters'}}
  />
  
  <div> Alerts </div>
  <div> &nbsp; &nbsp; @filterValue=this.filterValue </div>
  <Alerts
    @filterValue={{this.filterValue}}
  />
</div>

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"
  }
}