Add styled scrollbars to Firefox 64+ on Mastodon (if for some reason your instance isn't on mainline Mastodon)

readme.md

Add the following CSS using Stylus for Firefox https://addons.mozilla.org/en-GB/firefox/addon/styl-us/

mastodon-scrollbars-firefox.css

html,
.scrollable {
    /* Replace the color by the color of column headers for a better effect. */
    scrollbar-color: #313543 transparent;
    /* This is optional but I find the default scrollbars way too fat. */
    scrollbar-width: thin;
}