What I Wish I'd Figured Out Sooner

The default type of <button> is "submit" which is why a <button> in a <form> submits the form when clicked. Simply doing <button type="button"> removes this behaviour without the need for JavaScript. https://developer.mozilla.org/en-US/docs/Web/HTML/Element/button

Create a file called .hidden and fill it with a newline separated list of files. Works in Nautilus and Dolphin. Perfect for ~/snap.