Userscript to access engineering options in "WNC T-Mobile Internet 5G Home Office" ODU/Modem. Code might be shit because I don't know JS and it was generated by ChatGPT

tmobilewnc.user.js

// ==UserScript==
// @name         Add Engineering Mode Menu
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  Inject engineering mode submenu to the menu
// @author       You
// @match        *://192.168.0.1/*
// @grant        none
// ==/UserScript==

(function () {
    'use strict';

    const targetID = 'cssmenu'; // ID of the target <li>
    const submenuID = 'subMenu_system_eng'; // ID of the submenu
    const newBlock = `
        <li id='subMenu_system_eng' class='has-sub' style="display:block">
            <a>Engineering Mode</a>
            <ol>
                <li id="leftmenu_system_eng_general"><a onClick="return loadHTML('/system/system_eng_general.html');"><span>General</span></a></li>
                <li id="leftmenu_system_eng_lte_ca"><a onClick="return loadHTML('/system/system_eng_lte_ca.html');"><span>LTE CA Info</span></a></li>
                <li id="leftmenu_system_eng_rf_band"><a onClick="return loadHTML('/system/system_eng_rf_band.html');"><span>RF Band Info</span></a></li>
                <li id="leftmenu_system_eng_log2device"><a onClick="return loadHTML('/system/system_eng_log2device.html');"><span>On-Device Logging</span></a></li>
                <li id="leftmenu_system_eng_log_collector"><a onClick="return loadHTML('/system/system_eng_log_collector.html');"><span>Logs Collector</span></a></li>
                <li id="leftmenu_system_device_tr069"><a onClick="return loadHTML('/system/system_device_tr069.html');"><span>TR-069</span></a></li>
            </ol>
        </li>`;

    const observer = new MutationObserver(() => {
        const targetElement = document.getElementById(targetID);
        if (targetElement) {
            const ul = targetElement.querySelector('ul');
            if (ul && !document.getElementById(submenuID)) {
                ul.insertAdjacentHTML('beforeend', newBlock);
            }
        }
    });

    observer.observe(document.body, { childList: true, subtree: true });
})();