Documentation
Booking page
This section only applies if the module CRM is active.

Open a booking and click the 'Create order' button in the action block. You must have the appropriate permissions to do this.
The order dashboard will open. In the 'Order details' block, the price lines from the reservation are converted into order lines. Lines can be added to the order block, and a new block with new order lines can also be added.

The ‘action_booking_createorder’ right is required to create orders from booking pages.