Transmutation can be used on matter
I see a lot of people doubting it can be done or even thinking it can’t be done at all. I think it comes from Wing’s explanation, but he was incomplete about almost all categories in his explanation, so it shouldn’t be taken as an argument to define the limits of what a specific category can do.
I’ll demonstrate you can transmute matter with elementary nen logic and examples.
The first argument would be the water divination test. Killua changed the taste of water, so he effectively changed matter. Honestly I could stop my argument here as it’s a good enough proof that transmutation can affect matter, but i’ll develop a bit.
All categories can be used on aura AND aura-infused matter, transmutation is no exception. With emission you can detach your aura from your body, and by infusing aura into an object you can detach it from its container. With conjuration you can create a physical object with aura, but you can also impose rules on an existing space or conjure from existing matter. With manipulation you can give orders to your aura alone, and by proxy you can give orders to what your aura is infused in. So transmutation can alter shape and properties of aura, and what aura is infused in.
Be logical, you really think that a transmuter couldn’t infuse his aura in a wood stick, and change the shape of his aura while it’s infused in the stick, consequently changing the shape of the stick ? Sure it would be more difficult than just shaping aura alone but it perfectly follows the rules of nen.
We even have several examples in the manga, some aren’t confirmed but can be easely deduced. Youpi is a confirmed pure transmuter, his whole thing is to shape his body, and no it’s not just his ant and magical beast physiology, even if it helps. You clearly see him muster aura multiple times to change shape, explode and transform. You also see it when Meruem uses Youpi’s ability.
Those who aren’t confirmed but are highly probable : Bisky, unconsciously shaping her body to look like she does in exchange of reduced strength; Porcupine, changing the properties of his hair to make them soft and bouncy, or hard as needles; Worm, making the ground softer by contact to be able to dive and swim in it.
Just remembered Tubeppa transmuter nen beast can synthesize various drugs and chemicals inside its body, so that’s also one.
I have a couple more points but i’ll stop here. English isn’t my first language so sorry if it’s not clear or easy to read.