on the flipside, if you want this to persist regardless of what theme you're using, it's not difficult at all to make your own quick plugin with almost all the same code (excepting the plugin header), and have the shortcode persist across themes. Plugins can very much be individual single purpose functions.php files that you have an extra step to take in activating.
I'm a Software Engineer in Poland, working in my own small company. I built a lot of projects with PHP and other technologies connected with web development (JS, HTML5, Laravel, WordPress, CSS).
on the flipside, if you want this to persist regardless of what theme you're using, it's not difficult at all to make your own quick plugin with almost all the same code (excepting the plugin header), and have the shortcode persist across themes. Plugins can very much be individual single purpose functions.php files that you have an extra step to take in activating.
Worth consideration.
You're right! This tip is for beginners and I didn't wanted to make a mess in their head. 😁