In 'Settings/Users/Access management', enable the right: 'Manage the service flow with courses (next buttons)'.

Next buttons organize your order in separate courses to streamline the process with your kitchen (ex: starters, then main courses, then desserts).
The waiter can print a kitchen ticket for only one course of the order.

You can use up to five next buttons.
If you click on 'Next X' button, products are added to the sale in the X course.
To claim your kitchen for the X course (print products from the X course), click on the 'Next X' button and then on the 'Fire next X' button.

You can change the labels on your Next buttons with a CSS code (more information).