Set elements in Workflowcontainer during the Process

Hello Community,

i was searching a lot in the internet for a fitting solution of my problem. The Problem is i want to set 1 Element of the Workflowcontainer via ABAP Class. I need that Parameter for a switch in the Workflowprocess:

In the Switch:

In the Activity "Kennzeichen lesen für Vertretung Ja/Nein" im using the Task(ABAP Class and Method):

The Dataflow for the Task:

I think till this moment its all right. If not please tell me

In the Class ZCL_LR_WORKFLOW_CONTROL im setting the Parameter to 'X'.

During Debugging i can see the Elements doesnt get transfered.. Only the "BLA" Test Variable.

If im looking at the Transaction "SWI1" the Containerelement _WORKITEM.WORKITEMID is not inital but at the runtime it is inital why?

I hope you can help me or give me any tips for this problem

Kind Regards