Creating an order with multiple non-taxable and taxable products is available in Floranext and has been enabled for all shops. Here's how it works:
Create the Order
On the Take Order screen, once you add the product to the order, make sure the column 'Tax' in the Order Summary section shows unchecked, the item is not taxable.
Also, note when adding a POS or Website Product, you can choose whether that product should have tax or not by default so you can quickly add the common product to an order.