script.user.js

// ==UserScript==
// @name         RED Sticky Settings Button
// @namespace    https://savagecore.eu
// @version      0.2.1
// @description  Submit button on settings page follow as you scroll
// @author       SavageCore
// @require      https://greasemonkey.github.io/gm4-polyfill/gm4-polyfill.js
// @include      http*://redacted.ch/user.php?action=edit&userid=*
// @include      http*://apollo.rip/user.php?action=edit&userid=*
// @include      http*://notwhat.cd/user.php?action=edit&userid=*
// @grant        GM_addStyle
// @grant        GM.addStyle
// ==/UserScript==

(function() {
    'use strict';

     var css = "#settings_sections #submit{margin: 3px 0 15px 0;position: fixed;bottom: 0;width: 100px;}";
     GM.addStyle(css);
})();