PhD Student in Mathematics at Indiana University
You can find all my lecture notes in Overleaf.
I type my lecture notes using VSCode in LaTeX-Workshop. I use the HyperSnips extension to create snippets that lets me type lecture notes fast. I use the GlassIt extension to make my editor transparent, as I believe the editor looks more beautiful that way.
You can see a demo here:
My setup was inspired by sleepymalc.