i would like to see a new solid in the next update, one of my ideas are plexiglass, durable, shatters under high pressure, good in water and melts like wax but harder to melt and it dries quicker. Another element is a gas but i would like to see Helium, a gas lighter than air so it floats up, it is good for trigering the red wall if you were to release it and get interesting. THIS ONE IS FUN: Sulfer hexaflouride. This is the opposite of helium, it is 6 times denser than air so its a gas that floates down, it is not very soluble in water but it is soluble when incountered by a plant (it is a greenhouse gas) these two gasses are not flamable but everything in TPT does not have to go boom to be interesting. Those are my ideas
They are not useful enough to be in TPT, sorry, TPT has an element limit and when the elements acan be achieved through others there is no reason to make them, its probably not happening so you could learn how though.