To make pre-orders optional while booking for auto-confirm bookings, in your Pre-order menu of the booking type ensure the minimum order option is set to £0 for this to work.
Follow the below steps:
Click Settings, Sites and select the site.
Click Booking type and select the booking type.
Scroll down to Pre-order Settings and select While Booking.
Then in Pre-order menus, when you add the menu, set the minimum order section option to £0.
Finish the other settings as required.
Click Save.
🤓Note: When you test you can see pre-order are not a requirement. If you add multiple menus ensure all of them have the minimum order set to £0 as well.