OpenCart 3.0.2.0 уровень 3 подкатегории

Попробуй это:

контроллер:
Каталог \ контроллер \ Common \ menu.php

<?php
class ControllerCommonMenu extends Controller {
public function index() {
$this->load->language('common/menu');

// Menu
$this->load->model('catalog/category');

$this->load->model('catalog/product');

$data['categories'] = array();

$categories = $this->model_catalog_category->getCategories(0);

foreach ($categories as $category) {
if ($category['top']) {
// Level 2
$children_data = array();

$children = $this->model_catalog_category->getCategories($category['category_id']);

foreach ($children as $child) {

// Level 3
$grandchildren_data = array();

$grandchildren = $this->model_catalog_category->getCategories($child['category_id']);

foreach ($grandchildren as $grandchild) {

$grandchild_filter_data = array(
'filter_category_id'  => $grandchild['category_id'],
'filter_sub_category' => true
);

$grandchildren_data[] = array(
'name'  => $grandchild['name'] . ($this->config->get('config_product_count') ? ' (' . $this->model_catalog_product->getTotalProducts($grandchild_filter_data) . ')' : ''),
'href'  => $this->url->link('product/category', 'path=' . $category['category_id'] . '_' . $grandchild['category_id'])
);
}$filter_data = array(
'filter_category_id'  => $child['category_id'],
'filter_sub_category' => true
);

$children_data[] = array(
'name'  => $child['name'] . ($this->config->get('config_product_count') ? ' (' . $this->model_catalog_product->getTotalProducts($filter_data) . ')' : ''),
'href'  => $this->url->link('product/category', 'path=' . $category['category_id'] . '_' . $child['category_id']),
'children' => $grandchildren_data,
);
}

// Level 1
$data['categories'][] = array(
'name'     => $category['name'],
'children' => $children_data,
'column'   => $category['column'] ? $category['column'] : 1,
'href'     => $this->url->link('product/category', 'path=' . $category['category_id'])
);
}
}

return $this->load->view('common/menu', $data);
}
}

Посмотреть:
Каталог \ вид \ тема \ умолчанию \ шаблон \ Common \ menu.twig

{% if categories %}
<div class="container">
<nav id="menu" class="navbar">
<div class="navbar-header"><span id="category" class="visible-xs">{{ text_category }}</span>
<button type="button" class="btn btn-navbar navbar-toggle" data-toggle="collapse" data-target=".navbar-ex1-collapse"><i class="fa fa-bars"></i></button>
</div>
<div class="collapse navbar-collapse navbar-ex1-collapse">
<ul class="nav navbar-nav">
{% for category in categories %}
{% if category.children %}
<li class="dropdown"><a href="{{ category.href }}" class="dropdown-toggle" data-toggle="dropdown">{{ category.name }}</a>
<div class="dropdown-menu">
<div class="dropdown-inner"> {% for children in category.children|batch(category.children|length / category.column|round(1, 'ceil')) %}
<ul class="list-unstyled">
{% for child in children %}
<li><a href="{{ child.href }}">{{ child.name }}</a>
{% if child.children %}
<ul>
{% for children in child.children %}
<li><a href="{{ children.href }}">{{ children.name }}</a></li>
{% endfor %}
</ul>
{% endif %}
</li>
{% endfor %}
</ul>
{% endfor %}</div>
<a href="{{ category.href }}" class="see-all">{{ text_all }} {{ category.name }}</a> </div>
</li>
{% else %}
<li><a href="{{ category.href }}">{{ category.name }}</a></li>
{% endif %}
{% endfor %}
</ul>
</div>
</nav>
</div>
{% endif %}

Наконец, вам может понадобиться очистить кеши, кеш веток, кеши ocmod и т. Д.