Нужно еще в admin/controller/catalog/category.php примерно на 366 строке после кода
if (isset($this->request->post['category_description'])) {
$data['category_description'] = $this->request->post['category_description'];
} elseif (isset($this->request->get['category_id'])) {
$data['category_description'] = $this->model_catalog_category->getCategoryDescriptions($this->request->get['category_id']);
} else {
$data['category_description'] = array();
}
добавить (у меня переменная descript) следующий код:
if (isset($this->request->post['category_descript'])) {
$data['descript'] = $this->request->post['category_descript'];
} elseif (isset($this->request->get['category_id'])) {
$data['category_descript'] = $this->model_catalog_category->getCategoryDescriptions($this->request->get['category_id']);
} else {
$data['category_descript'] = array();
}