This script will add a button next to "import/create playlist" that allows you to add videos without searching for them

yt-workaround.user.js

// ==UserScript==
// @name         Plug.dj YT API Key workaround
// @namespace    https://plug.dj?refuid=4613422
// @version      1.3.3
// @author       WiBla (contact.wibla@gmail.com)
// @description  This script will add a button next to "import/create playlist" that allows you to add videos without searching for them
// @downloadURL  https://gist.github.com/WiBla/ad1aa9a98949c624cd2886c1a25b5feb/raw/8d83fc7bb1ac77f8ff9494023991e21e5599ec56/yt-workaround.user.js
// @updateURL    https://gist.github.com/WiBla/ad1aa9a98949c624cd2886c1a25b5feb/raw/8d83fc7bb1ac77f8ff9494023991e21e5599ec56/yt-workaround.user.js
// @include      *://plug.dj/*
// @include      *://*.plug.dj/*
// @exclude      *://*.plug.dj/_/*
// @exclude      *://*.plug.dj/@/*
// @exclude      *://*.plug.dj/!/*
// @exclude      *://*.plug.dj/about
// @exclude      *://*.plug.dj/ba
// @exclude      *://*.plug.dj/forgot-password
// @exclude      *://*.plug.dj/founders
// @exclude      *://*.plug.dj/giftsub/*
// @exclude      *://*.plug.dj/jobs
// @exclude      *://*.plug.dj/legal
// @exclude      *://*.plug.dj/merch
// @exclude      *://*.plug.dj/partners
// @exclude      *://*.plug.dj/plot
// @exclude      *://*.plug.dj/privacy
// @exclude      *://*.plug.dj/purchase
// @exclude      *://*.plug.dj/subscribe
// @exclude      *://*.plug.dj/team
// @exclude      *://*.plug.dj/terms
// @exclude      *://*.plug.dj/press
// @grant        none
// @run-at       document-end
// ==/UserScript==

/* global $, gapi, API */
(function() {
    'use strict';

    // Because plug.dj hides the interface while loading, this is necessary
    // We can't just use document.readyState ($.ready)
    function plugReady() {
        return typeof API !== 'undefined' && API.enabled && typeof jQuery !== 'undefined' && typeof require !== 'undefined';
    }
    function autoReload() {
        if (!plugReady()) {
            setTimeout(autoReload, 200);
        } else {
            init();
        }
    }
    function init() {
        window.gapi.client.setApiKey('AIzaSyD--___tekD3NI_-Sj8cAnNyuDKFmdtOkM');
        var pl = {}, media = {};

        function convert_time(duration) {
            var a = duration.match(/\d+/g),
                indexOfH = duration.indexOf('H'),
                indexOfM = duration.indexOf('M'),
                indexOfS = duration.indexOf('S');

            switch(true) {
                case indexOfM >= 0 && indexOfH == -1 && indexOfS == -1:
                    a = [0, a[0], 0];
                    break;

                case indexOfH >= 0 && indexOfM == -1:
                    a = [a[0], 0, a[1]];
                    break;

                case indexOfH >= 0 && indexOfM == -1 && indexOfS == -1:
                    a = [a[0], 0, 0];
                    break;
            }

            duration = 0;

            switch(a.length) {
                case 1:
                    duration = duration + parseInt(a[0]);
                    break;

                case 2:
                    duration = duration + parseInt(a[0]) * 60;
                duration = duration + parseInt(a[1]);
                    break;

                case 3:
                    duration = duration + parseInt(a[0]) * 3600;
                    duration = duration + parseInt(a[1]) * 60;
                    duration = duration + parseInt(a[2]);
                    break;
            }

            return duration;
        }
        function completeMedia() {
            $.ajax({
                url: `https://www.googleapis.com/youtube/v3/videos?id=${media.cid}&key=${gapi.config.get().client.apiKey}&part=snippet,contentDetails`,
                type: 'GET',
                success: (data) => {
                    media.author = data.items[0].snippet.title.split('-');

                    // Video's title contains a "-" so parse it
                    if (media.author.length) {
                        media.title = media.author[1].trim();
                        media.author = media.author[0].trim();
                    } else { // Otherwise, use the channel's name as author..
                        media.title = media.author[1].trim();
                        media.author = data.items[0].snippet.channelTitle;
                    }


                    media.image = data.items[0].snippet.thumbnails.default.url;
                    media.duration = convert_time(data.items[0].contentDetails.duration);
                    media.format = 1;
                    media.id = -1;

                    addMedia();
                },
                error: () => alert('YT API didn\'t reply, is your key still valid?')
            });
        }
        function addMedia() {
            $.ajax({
                url: `/_/playlists/${pl.id}/media/insert`,
                type: 'POST',
                data: JSON.stringify({
                    media: [media],
                    "append": false
                }),
                contentType: 'application/json',
                success: () => alert('Media added! You might need a refresh to see it.'),
                error: (err) => {
                    if (err.responseJSON.status === 'maxItems') {
                        alert('This playlist is full!');
                    } else alert('Sorry, the media couldn\'t be added.');
                }
            });
        }
        function extractCID(cid) {
            return cid.replace(/(?:https?:)?(?:\/\/)?(?:[0-9A-Z-]+\.)?(?:youtu\.be\/|youtube(?:-nocookie)?\.com\/\S*?[^\w\s-])((?!videoseries)[\w-]{11})(?=[^\w-]|$)(?![?=&+%\w.-]*(?:['"][^<>]*>|<\/a>))[?=&+%\w.-]*/gi, '$1');
        }
        function askCID() {
            media.cid = prompt(`Importing in ${pl.name}:\nVideo\'s link:`);
            if (!!media.cid === false) return;

            media.cid = extractCID(media.cid);
            completeMedia(media);
        }

        let found = false;
        function findPlaylist() {
            if (found) return askCID();
            pl.name = prompt('In which playlist do you wish to add the song?\nName must be exactly the same');
            if (!!pl.name === false) return;

            $.ajax({
                url: '/_/playlists',
                success: (data) => {
                    data.data.forEach((playlist, i, a) => {
                        if (playlist.name === pl.name) {
                            if (playlist.count === 200) {
                                alert(`${pl.name} is full!`);
                            } else {
                                pl.id = playlist.id;
                                found = true;
                                askCID();
                            }
                        }
                        if (i + 1 >= a.length && !found) {
                            if (confirm(`${pl.name} couldn't be found. Do you whish to add the live in "${playlist.name}"?`)) {
                                pl = playlist;
                                askCID();
                            }
                        }
                    });
                }
            });
        }

        var $grabBtn = $(`<div id="playlist-import" class="button" title="CTRL + Click to change playlist">
                              <i class="fa fa-plus-circle"></i>
                              <span>YT Grab+</span>
                          </div>`);

        $grabBtn.click(function(event) {
            found = event.ctrlKey ? false : found;
            findPlaylist();
        });

        $('.playlist-buttons-import-create').append($grabBtn);
        console.log('yt-workaround loaded! You\'ll need to refresh to deactivate it');
    };

    autoReload();
})();