Depending upon your security permissions and whether records
have been marked for deletion, you can delete records from both active
and inactive workflow processes.
Deleting inactive workflow process records
Process records can be deleted if the process has not been
activated or enabled, and no records have been routed through the
process.
Marking workflow process records for deletion
You can identify records that can be deleted when you create
a workflow process. Records that have been marked can be deleted once
the workflows they are part of have stopped.