RE: Workflow history details report
Getting the originator and approver(s) via step can be taken from the WFI10002, WFI10003 and WFI10004 tables using a WorkflowInstanceID and WorkflowStepInstanceID values for each workflow submitted for approval.
Linking them with other can be a little more complicated.
It kind of depends on whether you're referring to the Payables Invoice Approval workflow or the Payables Batch Approval workflow types?
If PM Batch Approval, it may make sense that the WF History report doesn't show voucher numbers in a batch.
That being said, PM Trx Approval primarily uses PM10000 table with the above WFI tables, and then PM Batch Approval uses primarily SY00500 until posted, then PM80100.
Using these tables, you may be able to put together a SQL script to pull all the information you want/need in a report for the auditors, then use that in a SmartList report or other type of report to be able to pull again and again in the future for the same reasons.
Thanks