Is It Possible to Reduce the Vertical Length of the Chin?

Yes it is possible to decrease the vertical height of the chin. There are a number of standard proceedurs for this .  Sliding osteotomies and / or segmental osteotomues can accoimplish this. However these are relatively big operations with prolonged periods of post operative swelling ( 2 to 4 months ) and occasional problems will numbness afterwards. I have also done in the past a proceedure where I grind down the bone with a cutting burr and avoid breaking any bone. This works nicely if only a small amount of bone needs to be removed

I was hoping you had front and side view pictures to get a better sense of what you meant.

Your chin may appear long due to bony changes, excessive soft tissue, lax skin or a combination. Knowing the cause and the overall shape of your face, for a balanced look, will help determine the best course of action to achieve a reduction in the length of your chin.

Best to consult with a facial reconstructive surgeon or oral maxillofacial surgeon in your area who specializes in genioplasty/ chin work.

Good Luck!