From the original post:

> There, I ex­plained my work­flow of tak­ing lec­ture notes in LaTeX using Vim and how I draw fig­ures in Inkscape.

Looks like the author was using Inkscape earlier but may have switched to something else recently. You can draw impressively beautiful diagrams in LaTeX with TikZ although it can be a lot of work to do so with TikZ which would make it difficult for live note taking.