If a client has booked in for a colour and finish but you then decide they need a treatment or a toner then you can adjust the bill easily so when you check out it is all correct.
To make changes to a booking, simply click anywhere on the appointment to surface the modal. Click 'edit booking':
This will open the booking window where you can add additional services using the 'add service' button:
Once you have selected the service, it will appear on the booking window where you can adjust the pricing and timing:
Once you have saved this change, the updated services will appear in your calendar: