Hi Mahmoud,
I am also have doubt on this functionality. In the field service module I believe following are the steps in GP
1. Service call entry
2. Parts required
3. Inventory requirement entry to allocate the parts to service Engineer sits
4. In transit shipment for transfer the qty to Engineer site
5. Then, Service completion and invoicing
I have doubt in step 3, functionally, how the way that process will affect the inventory. Could you please elaborate?