Tampermonkey Script to "pop out" toot composition for Mastodon

// ==UserScript==
// @name         Koyu.space embiggener
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  try to take over the world!
// @author       You
// @match        https://koyu.space/*
// @grant        none
// ==/UserScript==
(function() {
    'use strict';

    // Your code here...
    window.tm_embiggen = function() {
        document.getElementById('tm_embiggen_box_container').style.display = 'block';
        document.getElementById('tm_embiggen_box').value = document.getElementsByClassName('autosuggest-textarea__textarea')[0].value;
    };

    window.tm_ensmallen = function() {
        var native_textarea = document.getElementsByClassName('autosuggest-textarea__textarea')[0];
        var last_value = native_textarea.value

        native_textarea.value = document.getElementById('tm_embiggen_box').value;

        var tracker = native_textarea._valueTracker;
        if (tracker) {
            tracker.setValue(last_value);
        }
        native_textarea.dispatchEvent(new Event('input', { target: native_textarea, bubbles: true }));

        document.getElementById('tm_embiggen_box_container').style.display = 'none';
    };

    var div = document.getElementsByClassName('composer--options');
    if (div.length != 1) return;
    div = div[0];

    var big_button = document.createElement('button');
    big_button.classList = ['text-icon-button'];
    big_button.style = 'line-height: 27px; width: 23.1429px;';
    big_button.addEventListener('click', window.tm_embiggen);
    big_button.innerHTML = 'Big';

    var modal = document.createElement('div');
    modal.id = "tm_embiggen_box_container";
    modal.style = 'display: none; position: absolute; width: 40%; box-sizing: border-box; top: 25%; left: 30%; height: 450px; padding: 20px; background-color: black; border: 2px solid lightslategray; border-radius: 20px;';

    var text = document.createElement('textarea');
    text.id = 'tm_embiggen_box';
    text.style = 'width: 100%; height: 80%; box-sizing: border-box; padding: 10px; font-family: sans-serif; font-size: 16px; border: 0; border-radius: 6px; outline: none !important; resize: none;';

    var button = document.createElement('button');
    button.addEventListener('click', window.tm_ensmallen);
    button.style = 'margin-top: 10px; font-size: 16px; border: 0; border-radius: 5px; padding: 8px 25px; background-color: mediumseagreen; color: white;';
    button.innerHTML = 'Close';

    div.appendChild(big_button);
    modal.appendChild(text);
    modal.appendChild(button);
    document.body.appendChild(modal);
})();