For a math conversion tool, it's essential that Goodnotes should be able to recognize every mathematical or science symbol/sign. Simple symbols like the mathematical “therefore” symbol, ∴ , can't be recognized, making writing and converting one's math's notes a challenge especially in academic writing. Now I realize there are a lot of symbols out there, but one way to go about it is to take a look at the comprehensive lists at ctan.org. They have comprehensive list of every LaTeX symbol, which pretty much equates to every math symbol that can be indentified for conversion. I've attached one such file. Hopefully this helps.