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.

When opening a sale, the 'Direct' section is selected by default.
To add a course, click on the 'Next +' button under the sale details and add products. These products will be added to the newly created Course section.
To add products to an existing Course section, select the desired 'Next X' line on the ticket and add the products.

To claim the X course to your kitchen (print products from the X course), select the 'Next X' line on the ticket, then click the 'Fire Next X' button.

You can rename the Next lines with a CSS code (more information).