Hi Ivar Hove,
If your Issue is pretain to Serial Number and Batch, then Both can be Determined at sales order level.
Consider Business Requirement. If Business agrees to maintain Serial Numbers in Sales order.
In Regard to Serial Number,
Add Serial Number Procedure SDAU in your Serial Number profile and in Incompletion log add serial number into it, then system won't allow you to go forward without serial number.
In regard to Batch Management.
Enable Automatic batch determination in sales order Item category, ensure configuration releated to bach management.
Regards,
Vairavan.