_config.php

<?php

use SilverStripe\Core\Config\Config;
use SilverStripe\Core\Manifest\ModuleResourceLoader;
use SilverStripe\Forms\HTMLEditor\HtmlEditorConfig;
use Silverstripe\Shortcodable\Shortcodable;

if (!defined('SHORTCODABLE_DIR')) {
    define('SHORTCODABLE_DIR', rtrim(basename(dirname(__FILE__))));
}

// enable shortcodable buttons and add to HtmlEditorConfig
$htmlEditorNames = Config::inst()->get(Shortcodable::class, 'htmleditor_names');
$jsFile = ModuleResourceLoader::singleton()->resolveURL('silverstripe/shortcodable:javascript/editor_plugin.js');
if (is_array($htmlEditorNames)) {
    foreach ($htmlEditorNames as $htmlEditorName) {
        HtmlEditorConfig::get($htmlEditorName)->enablePlugins(array(
            'shortcodable' => $jsFile,
        ));
        HtmlEditorConfig::get($htmlEditorName)->addButtonsToLine(1, 'shortcodable');
    }
}

// register classes added via yml config
$classes = Config::inst()->get(Shortcodable::class, 'shortcodable_classes');
Shortcodable::register_classes($classes);