First of all. This is not another "how do I exit vim?" shitpost.
I've been using (neo)vim for about two years and I started to notice, that I,m basically unable to use non-vim editors. I do not code a lot, but I write a lot of markown. I'd like to use dedicated tools for this, but their vim emulators are so bad. So I'm now stuck with my customized neovim, devoid of any hope of abandoning this strange addiction.
I don't know understand why you need markdown, but if you are so used to vim motions why not switch to latex instead. You wouldn't have to worry about katex support as well. This is an advice solely based on your need for katex support without understanding your needs.