Hello,
You can perform a view override (ordermarket / listing) and add a button/link to open the invoice popup.
The usage of the HikaShop popup helper would be better and regarding the url ; it's just
hikamarket::completeLink('order&task=invoice&type=full&cid='.(int)$order->order_id, true)
At the end you will have a similar button than the one in the toolbar while displaying the order details.
But please do not forget to add some checks in PHP regarding the HikaMarket ACL
if(hikamarket::acl('order/edit/invoice')) {
...
}
So you won't display the button if the vendor do not have the access.
Regards,