Seeing as we now have a master leather backpack formula, it would be nice to also have the master tannin formula so that one doesn't have to transmute yew leather tannin into thornwood leather tannin anymore.
I've tested a harvest knife and a sap spigot on some thornwood trees, and both tools harvest the correct ingredients. Surely adding a formula to the game and giving it to a cenotaph or something should be a relatively trivial task?