Hello organsRgreat,
There isn't a specific function for it, I'm afraid (although we do have it logged as enhancement request), but you could potentially turn all stops on to see which stops the scoped piston affected, and then do likewise with all of the stops off. Together those two tests would show the scope. (You could conceivably programme 'all stops on' and 'all stops off' to two spare combinations for the purpose.)
However, using the 'Registration | Export/view combinations as text listing' menu function (as you mentioned) would probably be the quickest method.