Hi,
That's because the translation key there is just "new". So if you can't set it to "new something" as it wouldn't work for all the places with that same translation key used on buttons to create other new things.
To avoid that, a solution could be to have two different translation keys for each of these buttons. But then it requires translation files to be updated for all these new translations.
Now for your own shop, it's relatively easier as you don't care about the translation files of the 40+ languages HikaShop supports.
So you can edit the file cart / listing.php and add at the top such code:
<?php if(!empty($this->toolbar['new'])) $this->toolbar['new']['name'] = JText::_('XXX');
where XXX is the translation key of the text you want for the new button of the carts listing. And then you can add that XXX translation key in each language files override area in the Languages tab of the HikaShop configuration.
Creating new carts is useful so that customers can have different carts and switch from one to the other. For example, they prepare a cart for their christmas gifts , another one for what they want to purchase next week and a third one for their birthday gifts.
For most customers, I'm sure one cart is enough for them. And even for most shops. But for shops like Amazon, it makes sense to be able to build several lists of products you would like to buy.