in the old greed island arc, bisky tells gon the nen categories he needs to master for his ability, she classifies rock as enhancement, paper as emission and scissors as transmutation
rock being enhancement is pretty self explanatory and so does paper being emission (cuz he wanted it to be long range) but the scissors thing is weird since transmutation only allows you to give nen the properties of another substance that means making nen sharp wouldn't be transmuting nen but enhancing it, as in enhancing the sharpness of nen, the only other way i can think of is making his nen super hot but considering killua had to electrocute himself to make his abilities, gon would have to scorch or burn himself, which we never see him do, you could argue that he could've gotten burned as a kid and maybe channeled that feeling but i dont think thats enough, what do y'all think
edit: after reading the comments, i was wrong about the enhancement thing, that was a misconception, but some of you (if not all) are saying "sharp" is an attribute/property, it is generally, but it doesnt fit the criteria for transmutation, something being sharp isnt a physical property or value something being sharp depends on the shape of its edge,
i was also wrong about the bisky's number thing and ging's hand bubbles, cuz now that i think about it, volume is a physical property , overall that was stupidness from me, but sharpness still doesnt stand as viable for transmutation, idk, nobody has given an actual explanation yet
edit 2: i dont think anyone said this but if they did kudos to them, gon can manipulate the density of his aura, and shape it into a blade, aka giving aura the same properties as a sword, sharp itself isnt a property but it can be made