Starting from version 6.21.07.28 you can pay a part of a bill on tab instead of the whole tab. This might be handy when a group is using a shared tab, and one of them wants to leave and pay their part of the bill. If you go to the tab, you have a new button ‘Split selected bill’ on top.
When you click this button, it will show all bill lines on the left. You can group them if you like (by bill, by person, …). Now you can multi-select all the products that you want to pay off and press the right arrow. If you want to remove bill lines again, just select the lines on the right, and press the left button.
When you select a bill line with a quantity of more than 1, it will ask you how many of these you want to move to the new bill.