Your blog post was about creating a self-signed TLS cert. mkcert is more than that, it creates the root CA first before creating self-signed certs and trusting them.
seems a way to gather all kinds of extra clutter on your box. keep notes of things you do :-) it just requires a txt editor present in most operating systems by default. if you document carefuly, you can even just add #!/bin/sh in the top to automate ;D but it's atleast honest comment :D
I freely admit I'm bad at keeping notes - I've tried various systems over the years (from wikis to nvalt to evernote etc) and hated them all for one reason or another. And there is a limit to the usefulness of scripting it all, because I'll soon forget what the script was for, the inevitable pitfalls, what to change if I'm on another machine and so on. So this sort of very simple and natural interface can be appealing to me. Mind, I'll probably forget I've installed it and in 6 months time I'll have the same problem and I'll google openssl again...