I am not sure I exactly understand your link between Maximo and SAP but fields you could look at utilising for SAP operations would be the Control Key and the Activity Type. The drawback of the Control Key for you may be that once a confirmation has been entered against an operation it cannot be changed (although this maybe an advantage). The disadvantage of Activity Type is that those entering confirmations can override the setting in the work order operation. I would start by looking at the Control Key.
The Standard Text Key field is another option for you.