Everyone who wears a belt knows the problem, it's neither short nor long enough to fit perfect and not getting in the way of your left elbow. Has anyone got a lifehack to fix the leftover part so it won't stick out anymore?
Cut it off.
You don't need it. It is thus useless to you. Further more, it seems to be getting in your way.
It may seem wasteful to cut if off. But you just don't need it.
But what is your plan? To suddenly gain a lot of weight? If you are underweight, and intending on doing so, then wait until you have done so before trimming your belt. If you are a healthy weight, then I suggest reconsidering your plan to gain more weight.
If you are concerned about reselling it or giving it away, then that would be overlyselfless, prioritising a possible future user over your current needs.
How to cut it:
Trace the curve on the end on to paper as a stencil, then trance back with a marker. Cut it with a sharp knife or a sturdy pair of scissors.
Cut it with sissors. Fold it and stich a hem on to stop it unraveling. Not too hard with a hand needle, but if you have a sewing machine, use it.
Cut and seal it like a rope. Heat up a old butter knife til it is red hot. Cut it, melting the ends shut. Dip fingers in water and mold it to a rounded edge. Or/And use a nail file to round it after it has cooled.
If it has metal top on the end. Then you will need to examine how it is attached. The ones on cloth belts can normally be opened up prior to cutting and folded back over after you have cut.
Metal ones can be reattached with rivets or superglue
If you wear a belt, your trousers probably have "buckles" (sorry i don't know how it would be called in English) to hold the belt so you can just tuck the leftover part into those. If you don't have that (then the belt will probably be less useful) or the buckles are to far away from each other so that the leftover part of the belt could be long enough to bother you, I would suggest using a rubber band that you put around your belt around the point where the leftover part ends. You then just have to tuck the ending part of the belt into this rubber band.
A great thing to do when a belt is too long is to use little elastic bands or 'rainbow looms' matching the color of your belt. Before putting on the belt put on the elastic bands to the side of the belt that has the buckle at its end. Then when you put on your belt slide the end of the belt through the bands so that extra part does not hang out and irritate you.
My Ex girlfriend was into clothing design. I had this problem and on some of my pants she moved the belt loop and on others she made a new belt loop from fabric she scavenged from inside hems. She learnt to do it from an old lady she worked for while she was studying who would charge less than $10 as it took less than 15 min. Maybe ask around some local alterations places.
If you buy a belt that's a couple inches too long, it gives you a little room to expand if needed, without being overly long. But let's say you do that and lose some weight and now you've got several extra inches.
My pants have about 6 inches (15 cm) between the front loops. My belt buckle is about 2 inches (5 cm) across, meaning I have about 4 inches (10 cm) of play. I buy the belt so the tip is about 1 inch (2.5 cm) sticks out the loop on my left (I put my belt in right to left, so it wraps around me and sticks out to the left), and I center the buckle right over my button/zipper area.
Now, let's say I get fat and add 2 inches (5 cm) to my waste size. I can shift my buckle to the left by the same 2 inches and the loop still holds the excess.
On the other hand, let's say I lose weight and remove 2 inches. Now I shift the buckle to the right and the original 1 inch is sticking out the left loop. This doesn't work as well with dress pants if you want to keep the buckle lined up with your zipper line, but it's nice for more casual wear. Even if you don't want it to be extremely offset, a little movement can help a lot.
Just get a belt that tucks behind the belt buckle.
It's my all time favorite and looks SUPER Clean. They are hard to find, but they exist. Adidas still makes some. https://www.amazon.com/dp/B005V04924/?coliid=I33JXCOADZ6K9B&colid=1KHFV1DG352XD&psc=0&ref_=lv_ov_lig_dp_it
EDIT and UPDATE: The generic name for this is a "cam lock" belt buckle. It does not use holes for length adjustment. A cam pinches the belt between two metal parts instead of using a "prong" that fits into holes at the end of the strap.
You may be able to purchase a replacement "keeper loop" https://smile.amazon.com/s?k=keeper+loop+belt
Another suggestion: somehow create your own replacement "keeper loop" (out of similarly colored fabric) ref: https://archive.triblive.com/news/find-a-fix-to-keep-belts-tip-from-flapping/