Hello Dieter,
MethodAPIActionSendToDesktopV2 does 2 things
A. Setting up the record so that it can be picked up by the method integration engine with the next sync
B. Pushing the record to Quickbooks
We have an issue with Step B which you are working around by doing a changes only sync, but we still need MethodAPIActionSendToDesktopV2 to do Step A. Below steps should sync sales orders fine without going through the process of updating fields.
1.Insert Sales Order
2.Insert Sales Order Line
3.Call MethodAPIActionSendToDesktopV2 for the SalesOrder RecordID
4.Perform full or changes only sync (you could also wait for the next auto sync)
If you are populating these 2 fields - Finalduedate and GenericName before Step 3, it should sync fine.