You can enable up to six custom addons to a new or existing delivery checkout.

Custom addons, for example, 'Gift wrapping', are not related to certain delivery options when enabled on delivery checkout level. But you can choose to make a custom addon available on delivery option level instead

1. Go to Maintenance > Delivery checkout.
   
   
2. When creating a new delivery checkout you enable custom addons on the New delivery checkout page. To enable custom addons on an existing delivery checkout, click the edit icon  to the left of the delivery checkout on the Delivery checkout page.
   
   
3. Click the edit icon to the left of an addon row in the Custom addons section.
   
   
4. Check the Preselected box if the addon should be automatically chosen in advance.
   
   
5. Check the Mandatory box if the addon should be required for the service.
   
   
6. Check the Available in delivery option box to make it possible to use the custom addon on delivery option level.
   
   

Note: If you click OK when leaving the Edit addon page, the addon is enabled even if you have not entered any information. If you have chosen to make a custom addon available on the delivery option level, you have to enable it for each delivery option where it is relevant.

In the API, custom addons behave exactly like carrier-specific ones, when set as available in delivery option. If custom addon is set to be available on checkout level, it will be returned on object root level.  

You disable a custom addon by clicking the delete icon to the left of the addon row.