A simple tampermonkey script for creating a playlist for all videos of a channel. Navigate to a video and click the button inside the tampermonkey. The code is written by gpt4o

PlayListCreatorForAllVideosOfAChannel.js

// ==UserScript==
// @name         Create A playlist full fill with all videos of a channel
// @namespace    http://tampermonkey.net/
// @version      1.0
// @description  Modify YouTube Channel ID and open new URL in foreground tab with button click
// @author       Your Name
// @match        https://www.youtube.com/*
// @grant        GM_registerMenuCommand
// ==/UserScript==

(function() {
    'use strict';
//Credits: https://www.youtube.com/watch?v=M-PJ10sdcYA
    
    function main() {
        const channelId = getChannelId();
        if (channelId) {
            const changedChannelId = changeChannelId(channelId);
            const videoUrl = getVideoUrl();
            if (videoUrl) {
                const newUrl = constructNewUrl(videoUrl, changedChannelId);
                openNewTab(newUrl);
            } else {
                console.log("Couldn't find the Video URL.");
            }
        } else {
            console.log("Couldn't get the Channel ID");
        }
    }

    function getChannelId() {
        const regex = /"channelId":"([^"]*)"/;
        const match = document.body.innerHTML.match(regex);
        return match ? match[1] : null;
    }

    function changeChannelId(channelId) {
        return channelId.substring(0, 1) + 'U' + channelId.substring(2);
    }

    function getVideoUrl() {
        const regex = /watch\?v=([^&]*)/;
        const match = window.location.href.match(regex);
        return match ? match[0] : null;
    }

    function constructNewUrl(videoUrl, changedChannelId) {
        return `https://www.youtube.com/${videoUrl}&list=${changedChannelId}`;
    }

    function openNewTab(url) {
        window.open(url, '_blank').focus();
    }

    GM_registerMenuCommand("Create A playlist full fill with all videos of a channel", main);

})();