min-scroll.js

// ==UserScript==
// @name         xCSS Minimalistic Scroll
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  try to take over the world!
// @author       You
// @match        http://*/*
// @match        https://*/*
// @grant        none
// @run-at       document-start
// @icon        https://t1.gstatic.com/faviconV2?client=SOCIAL&type=FAVICON&fallback_opts=TYPE,SIZE,URL&url=https://www.w3schools.com/
// ==/UserScript==

setInterval(()=>{
    if(!document.getElementById('xScroll'))
    {
        document.body.insertAdjacentHTML('afterend',`<style id="xScroll" type="text/css">
html::-webkit-scrollbar {
	width: 5px!important;
	height: 5px!important;
}
html::-webkit-scrollbar-thumb {
	background-color: #383838!important;
	border: 2px solid #484848!important;
	border-radius: 5px!important;
}
html::-webkit-scrollbar-track {
	background-color: transparent!important;
}
html::-webkit-scrollbar-thumb:hover {
	background: #282828!important;
}
html::-webkit-scrollbar-thumb:active {
	background: #181818!important;
}
html::-webkit-scrollbar-corner {
	background: #383838!important;
}
</style>`);
}
},100);