What can I do to decrease the length of my philtrum? (Photo)

From your picture, I feel you would be a perfect candidate for a lip lift procedure. As we get older we may start to notice areas of our bodies going south, breasts start to sag and we notice jowls appearing on our jawline. What you may also notice is the space between your nose and your upper lip may gradually start to widen. This is all due to gravity. Surgical enhancements like a lip lift or facelift can help restore our youthful look.
It is inevitable that our lips will begin the southward slide at some point, resulting in a thinner upper lip that looks like it’s flattening, lengthening or disappearing.
Up until now the only temporary solution for this would have been lip fillers but even then it may not give you the lift you want, and putting implants in would also not provide you with the result you desire. That’s where the lip lift procedure is becoming more and more popular. This procedure gives instant results and is permanent. It is also a very quick procedure and the downtime is minimal.
This surgery aims to reduce the distance between the top of the upper lip and the base of the nose. Surgery not only shortens the cutaneous lip (the skin between the nose and the red lip) but it also allows for a more prominent vermilion (the red portion of the lip), thus creating a perfect cupid’s bow.

You can consider a modified upper lip lift which would help to shorten your philtrum as well as roll your upper lip upwards somewhat to increase fullness. This is done by carefully removing tissue immediately below your nose. When done properly the scar is nearly invisible and it would help create the proportions you're looking for. Good luck!