Back in high school I used OneNote and had a pretty good MS equation editor setup. Most things can be done in a similar way to LaTeX, e.g. writing \theta for gr

Back in high school I used OneNote and had a pretty good MS equation editor setup. Most things can be done in a similar way to LaTeX, e.g. writing \theta for greek letters, writing a slash for fractions. With a few "replace with" "macros" I could write quite fast, probably faster than I can in LaTeX these days after about the same amount of practice, and almost never had to use the GUI. These days my notes are all Markdown with inline LaTeX for math. I haven't yet found an editor that support "global" LaTeX macros/shorthand. Things like matrices can be bit of a pain, but then I haven't written any since linear algebra.