disable_youtube_playlists.user.js

// ==UserScript==
// @name         Disable YouTube playlists
// @description  Remove playlist part from watched videos
// @namespace    https://gist.github.com/Maxr1998/f07175ad05ed5c783da9b98bceee61a6
// @downloadURL  https://gist.github.com/Maxr1998/f07175ad05ed5c783da9b98bceee61a6/raw/2b47f9d7949f95b1b6e50f3be79d49ac48f95af7/disable_youtube_playlists.user.js
// @updateURL    https://gist.github.com/Maxr1998/f07175ad05ed5c783da9b98bceee61a6/raw/2b47f9d7949f95b1b6e50f3be79d49ac48f95af7/disable_youtube_playlists.user.js
// @author       Maxr1998
// @version      0.1.1
// @match        *://*.youtube.com/*
// @icon         https://www.google.com/s2/favicons?domain=youtube.com
// @grant        none
// @run-at       document-start
// @license      GNU GPLv3
// ==/UserScript==

function redirect() {
    const listRegex = /&list=\w+&index=\d+/;
    if (window.location.href.indexOf('youtube.com/watch') > -1) {
        const previous = window.location.toString();
        const normalized = previous.replace(listRegex, '');
        if (previous !== normalized) {
            window.location.replace(normalized);
        }
    }
}

redirect();

let oldHref = document.location.href;

window.onload = function() {
    const bodyList = document.querySelector("body")
    const observer = new MutationObserver(function(mutations) {
        mutations.forEach(function(mutation) {
            if (oldHref != document.location.href) {
                oldHref = document.location.href;
                console.log('location changed!');
                redirect();
            }
        });
    });
    const config = {
        childList: true,
        subtree: true
    };
    observer.observe(bodyList, config);
};