As a retired martial arts instructor, I can't really say that being shorter gives you much of an advantage when targeting an opponent's belly...but it does mean you will have a lower center for gravity compared to larger opponents.

In grappling terms, this gives you a slight advantage in applying leverage for most shoulder throws. Your natural pivot point at the hip is lower than theirs so they will be top heavy compared to you.

Unfortunately, if your arms are proportional to your height, then larger opponents will have a reach advantage over you, which may negate the advantage you have due to your lower center of gravity. They will be able to keep you from closing the distance needed to apply your leverage.

But, if you happen to have unusually long arms relative to your height, then you can still get a hold of them before they can get a hold of you...and more effectively position them for a throw.