When I mount a strap-on type bow quiver onto my bow, sometimes there is excess strap hanging out when I’m through. Personally, I won’t cut it off, as I may use the quiver on another bow (recurve rather than longbow, perhaps) and may need the excess strap.
However, that little flapper-do can be a source of flapper-do noise when the bow is shot. I discovered this after “fixing” everything else on the bow and quiver to alleviate a bothersome racket. It seemed awfully loud to me anyway.
I’ve tried double-sided Velcro straps made for bundling wires, zip ties, and tape to hold the strap down. They all work, but this is so simple and easy.
I found these “Fuzz Sticks” in a department store hobby section once upon a time when I was helping with a grandson’s art project. We called them pipe cleaners in my youth. They are inexpensive, flexible, fairly sturdy, very easy to work with, and very quiet as well. I keep a few around for other little tie up jobs, or for a temporary zipper pull, if needed.