Aside from using the UI to do a WIP adjustment, are there any other alternatives in order to do a WIP adjustment
I don't know any.
You could use XOG to create transactions en masse.
These transactions could have the same monetary effect as WIP adjustments that is change the monetary amount and applied to the same investment object and associated with the same or other recource etc. but they would not change the status of the orginal transactions like the WIP adjustment can do. The original ones would display just as before even if there are new transactions which change the total effect.
Currently, the application does not provide for WIP Adjustment on exsting transactions in WIP.
One alternative, as mentioned by 'urmas' is to create new transactions with same exact date, resource, task, project to 'offset' the original transaction.
Be careful not to create a net 'negative' amount by transaction date or you will encounter data discrepancy issues when posting back to the project.
"Currently, the application does not provide for WIP Adjustment on exsting transactions in WIP"
sounds like XOG or something with that is missing eg
Currently, the application does not provide XOG for WIP Adjustment on exsting transactions in WIP
Retrieving data ...