TamperMonkey UserScript to mod Zendesk's TinyMCE with custom CSS from your Zendesk Help Center

Zendesk TinyMCE custom CSS.user.js

// ==UserScript==
// @name         Zendesk TinyMCE custom CSS
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  *** Replace "servantsystems" with your "Help Center" name so this can retrieve your custom CSS ***
// @author       BrianLaLonde
// @match        https://*.zendesk.com/knowledge/articles/*
// @require      https://code.jquery.com/jquery.min.js
// @require      https://gist.github.com/raw/2625891/waitForKeyElements.js
// @grant        none
// ==/UserScript==

(function() {
'use strict';
    var CSSUrlStr = "";
    //get the public root of our knowledgebase and get the CSS from it
    $.get("https://servantsystems.zendesk.com/hc/en-us", function(response) {
        var indexScript = response.indexOf('<link rel="stylesheet" type="text/css" href="//p');
        if (indexScript < 0)
            alert("MonkeyScript: CSS not found");
        else {
            var indexScriptStart = response.indexOf('//p', indexScript);
            var indexScriptEnd = response.indexOf('"', indexScriptStart);
            CSSUrlStr = response.substring(indexScriptStart, indexScriptEnd);
        }
        waitForKeyElements ("#mceu_20", ModTheEditor);
    });

    //do some mods of the knowledgebase editor
    function ModTheEditor (jNode) {
        $('iframe').contents().find("link").remove();
        $("iframe").contents().find("head").append('<link rel="stylesheet" href="https:'+CSSUrlStr+'">');
        tinymce.activeEditor.dom.addClass('tinymce', 'article-body');
        document.querySelector('._-src-components-ContentEditor-index---titleInput---1xUD7').style.margin = 0;
        document.querySelector('._-src-components-ContentEditor-index---metadata_section---3Rg_3').style.margin = 0;
    }
})();