I'm not so sure why is this a 'hidden-city' situation? You didn't provide your full route but if I get it right, you have a ticket AAA-AMS-BBB r/t, and you want to skip the AMS-AAA segment on the return trip, there is no issues with that as there are no further legs on your journey and so nothing will be cancelled.

The only catch is if you have checked-in luggage, getting KL to short-check it to AMS might not be possible.