Move GMailMessageViewToolbarButtonsToTopToolbar.user.js

// ==UserScript==
// @name         Move GMail Message View Toolbar Buttons To Top Toolbar
// @namespace    https://greasyfork.org/en/users/85671-jcunews
// @version      1.0.2
// @license      AGPLv3
// @author       jcunews
// @description  https://www.reddit.com/r/userscripts/comments/r5m0rc/move_gmail_compose_buttons_to_top_of_conversation/
// @match        https://mail.google.com/mail/*
// @grant        none
// @run-at       document-end
// ==/UserScript==

(() => {
  if (!document.body) return;
  document.body.insertAdjacentHTML("beforeend", '<style> .cf.wS { display: none } </style>');
  (new MutationObserver(
    (btnTemplate, btns) => {
      if ((btns = document.querySelectorAll(".amn > .ams")).length) {
        if (
          (btnTemplate = document.querySelector(".bzn .G-Ni:nth-child(2)")) &&
          !document.querySelector(".btnShortcut")
        ) {
          btns.forEach((btn, i, newBtn) => {
            newBtn = btnTemplate.cloneNode(true);
            newBtn.dataset.btnindex = i;
            newBtn.classList.add("btnShortcut");
            newBtn.firstElementChild.removeAttribute("act");
            newBtn.querySelector(".Bn").textContent = btn.textContent;
            newBtn.addEventListener("click", function(ev) {
              if (ev.button) return;
              ev.stopImmediatePropagation();
              ev.stopPropagation();
              ev.preventDefault();
              document.querySelectorAll(`.amn > .ams`)[this.dataset.btnindex].click();
            }, true);
            btnTemplate.parentNode.insertBefore(newBtn, btnTemplate);
          });
        }
      } else document.querySelectorAll(".btnShortcut").forEach(e => e.remove());
    }
  )).observe(document.body, {childList: true, subtree: true});
})();