1. in Preferences > Sales Orders > Field Customisation, the Shipping Type is there, and I believe it was added there automatically: if I change something, the change is reflected in Books - so it's linked;
2. however clicking on it to edit it gives error "Invalid value passed for relation entity or relation list name.";
3. in Configure Access for the field, everything is selected;
4. in Users & Roles > Roles > (i.e.) Dispatch, three is no way to allow reading for this custom module - it's absent.

I believe this is the main problem. The custom modules between the two apps are linked but only half way. Permissions for the modules are missing. The feature is in beta so I hope it may come later. Could you please confirm it, or offer a solution?