I love how Keyboard Maestro comes into play. Instead of some Markdown extension doing the conversion on render, the author selects and converts each equation manually. I think it's a good idea to keep MathML rather than LaTeX in Markdown source.
I have written an AutoHotkey script for my own use that does something similar, but for converting Markdown to HTML — so that I can write in Markdown, but fall back to embedded HTML easily if Markdown is not enough. Maybe I shall replace its pulldown_cmark backend with pandoc to get support for MathML.
There are numerous projects called "SVG Path Editor", among which this is the most advanced and usable one I've come across.