Twitter mobile: send message on enter https://greasyfork.org/en/scripts/20454-twitter-mobile-enter-to-send-message

twitter-mobile-enter-to-send-message.js

// ==UserScript==
// @name        Twitter Mobile - Enter to send message
// @version      0.4
// @description  This script allows user to send message by pressing the enter key on Twitter Mobile DM
// @author       himalay
// @namespace    https://himalay.com.np
// @include     *://mobile.twitter.com/messages/*
// @run-at document-end
// ==/UserScript==

document.addEventListener('keydown', function(e) {
    if (e.keyCode === 13 && !e.shiftKey) {
      document.querySelector('[data-testid="dmComposerSendButton"]').click();
        setTimeout(() => {
            document.querySelector('textarea').focus();
        }, 200);
      e.preventDefault();
    }
}, false);