Put this in a chrome bookmark url field and click on while on a youtube playlist to download a vlc playlist.

Youtube vlc playlist bookmarklet.js

javascript:(function () {

    function getUrlVars() {
        var vars = {};
        var parts = window.location.href.replace(/[?&]+([^=&]+)=([^&]*)/gi, function (m, key, value) {
            vars[key] = value;
        });
        return vars;
    }

    function getUrlParam(parameter, defaultvalue) {
        var urlparameter = defaultvalue;
        if (window.location.href.indexOf(parameter) > -1) {
            urlparameter = getUrlVars()[parameter];
        }
        return urlparameter;
    }

    function download(filename, text) {
        var element = document.createElement('a');
        element.setAttribute('href', 'data:text/plain;charset=utf-8,' + encodeURIComponent(text));
        element.setAttribute('download', filename);

        element.style.display = 'none';
        document.body.appendChild(element);

        element.click();

        document.body.removeChild(element);
    }

    var eTitle = document.getElementById('title');

    var sTitle = eTitle.getElementsByTagName('a').length > 0 ? eTitle.getElementsByTagName('a')[0].innerText : 'Playlist';

    var listId = getUrlParam('list', false);
    var list = [];
    var endPoints = document.getElementsByClassName('yt-simple-endpoint');

    for (i = 0; i < endPoints.length; i++)
    {
        let sHref = endPoints.item(i).href;
        if (sHref !== '' && sHref.indexOf('watch?') > 0)
        {
            if (listId !== false && sHref.indexOf('&list=' + listId) !== -1) {
                if (!list.includes(sHref)) {
                    list.push(sHref);
                }
            } else if (listId === false) {
                if (sHref.indexOf('&list') !== -1) {
                    sHref = sHref.substr(0, sHref.indexOf('&list'));
                }
                if (!list.includes(sHref)) {
                    list.push(sHref);
                }
            } else {
                continue;
            }


        }
    }

    var xmlDoc = document.implementation.createDocument(null, "playlist");
    xmlDoc.firstChild.setAttribute('xmlns', "http://xspf.org/ns/0/");
    xmlDoc.firstChild.setAttribute('xmlns:vlc', "http://www.videolan.org/vlc/playlist/ns/0/");
    xmlDoc.firstChild.setAttribute('version', "1");

    var title = xmlDoc.createElement('title');
    title.append(sTitle);
    xmlDoc.firstChild.append(title);

    var tracklist = xmlDoc.createElement('trackList');
    var extensions = xmlDoc.createElement('extension');
    var loc, trackextension, vlcid, vlcitem, tid;

    extensions.setAttribute('application', 'http://www.videolan.org/vlc/playlist/0');

    for (i = 0; i < list.length; i++)
    {
        track = xmlDoc.createElement('track');
        loc = xmlDoc.createElement('location');
        loc.textContent = list[i];

        trackextension = xmlDoc.createElement('extension');
        trackextension.setAttribute('application', 'http://www.videolan.org/vlc/playlist/0');

        vlcid = xmlDoc.createElement('vlc:id');
        vlcid.textContent = i;

        trackextension.append(vlcid);
        track.append(trackextension);
        track.append(loc);
        tracklist.append(track);

        vlcitem = xmlDoc.createElement('vlc:item');
        vlcitem.setAttribute('tid', i);
        extensions.append(vlcitem);
    }

    xmlDoc.firstChild.append(tracklist);
    xmlDoc.firstChild.append(extensions);

    var xmlText = '<?xml version="1.0" encoding="UTF-8"?>' + new XMLSerializer().serializeToString(xmlDoc);


    download(sTitle + '.xspf', xmlText);

}());