Grappling hooks have been made known to be a little overpowered, so an idea was suggested on the curse page to make it use ammo. Split up the grappling hook launcher and the hook into 2 items, and have to shoot and reload the grappling hook like a crossbow, or better yet, make the crossbow fire it to fit with vanilla a little better.

This issue is open for discussion.

I'm not sure hijacking the crossbow is a the best idea. Adding an ammo and the suggestions made in #21 i think is the best approach

That works for me.

I like the idea of grappling hook ammo. Something as simple as a "Grappling Hook" ammo that is crafted from, say, an Arrow, String and something else (Iron Bar?) would be excellent.

I personally enjoy the idea of hijacking the crossbow for this purpose, as it would give it some more utility outside of being a niche and generally weaker bow. One would need to figure out what happens when the crossbow is enchanted with Multishot, of course, but I find this to be an entertaining idea.~
As for a recipe for the ammunition, one rope, one iron ingot and two iron nuggets in a T shape would visually look like a grappling hook and would be suitably uncheap.~