Greasy Fork

(function() {
function add() {
document.querySelector("#root > div.sc-eXlDFz.fmdpDr > div:nth-child(1) > div.product > div.container > div.product-action-bar > div:nth-child(1) > button").click();
}

function tickBox() {
document.querySelector("#root > div.sc-eXlDFz.fmdpDr > div:nth-child(1) > div.product > div.container > div.create-listing > div:nth-child(5) > div.create-listing-checks > label:nth-child(2) > input[type=checkbox]").click();
}

function send() {
document.querySelector("#root > div.sc-eXlDFz.fmdpDr > div:nth-child(1) > div.product > div.container > div.create-listing > div.create-listing-btn-bar > button").click();
console.log("Complete");
}

function ok() {
document.querySelector("#root > div.sc-eXlDFz.fmdpDr > div:nth-child(1) > div.product > div.container > div.create-listing-confirm > button").click()
}

var btn = document.createElement("BUTTON");
btn.innerHTML = "Add to listing";
document.body.appendChild(btn);
document.querySelector("body > button").style.position = "fixed";
btn.addEventListener('click', () => {
add();
setTimeout(tickBox, 1000);
setTimeout(send, 1500);
setTimeout(ok, 2000);
});

That The Script

you wanna post wonderful explanation but it has some other ways solve this problems ... FlixTV Apk

I think you can use the library WaitForKeyElements.js:

waitForKeyElements.js - by BrockA [GitHub]
Read:
Comments: BrockA/waitForKeyElements.js

Import by adding:
// @resource waitForKeyElements https://gist.githubusercontent.com/BrockA/2625891/raw/9c97aa67ff9c5d56be34a55ad6c18a314e5eb548/waitForKeyElements.js

Library | onElementReady ES6 [GreasyFork Library
WaitForKeyElements.js : Examples [GitHub]