When a client is paying for their appointment on the day but also asking to rebook their next appointment & they want to pay a deposit, then you aren’t currently able to combine them into the one transaction, if the appointments are on separate dates. It’s unusual not to be able to group both payments together & pay it off as one card payment instead of getting the customer to pay each separately.
Also whenever you go to pay off an appointment & are prompted to rebook & then do, the option to pay off the appointment relates to the new appointment & can result in the wrong appointment being paid off.