how to be dropdown field of product_category

-- url of the page with the problem -- : localhost
-- HikaShop version -- : 3.3.0
-- HikaMarket version -- : 1.7.1
-- Joomla version -- : 3.8.5
-- PHP version -- : 7.0.0
-- Browser(s) name and version -- : chrome


I want to when i'm in add product , field of product_category be dropdown ( like select and option) or be namebox single . what should i do?

tnx
i want vendor just select one category but i not found any answer in this topic
but i have this code in productmarket > form:

$categories = null;
		if(!empty($this->product->categories))
			$categories = array_keys($this->product->categories);
		echo $this->nameboxType->display(
			'data[product][categories]',
			$categories,
			hikamarketNameboxType::NAMEBOX_MULTIPLE,
			'category',
			array(
				'delete' => true,
				'sort' => true,
				'root' => $this->vendorCategories,
				'default_text' => '<em>'.JText::_('HIKA_NONE').'</em>',
			)
		);

hikamarketNameboxType::NAMEBOX_MULTIPLE

hikamarketNameboxType::NAMEBOX_SINGLE

very thanks . it's worked