I think there is not any config option to turned on twig template debug in opencart 3.0.2.0.if wrong do correct and suggest solution to solve this.
{{ dump() }}
Try this: Go to system/library/template/Twig/Environment.php In $options array. Set 'debug' option to 'true' at the bottom add:
$this->addExtension(new Twig_Extension_Debug());