Replace the titles and urls with your own links!

Code:

// ==UserScript==
// @name         Lemmy Custom Navbar
// @namespace    http://tampermonkey.net/
// @version      0.1
// @author       https://lemmy.world/u/0485919158191
// @description  Adds a custom navbar to Lemmy with links to custom pages.
// @match        *://*/*
// @grant        none
// ==/UserScript==

(function () {
  'use strict';
   const isLemmy = document.head.querySelector("[name~=Description][content]").content === "Lemmy";
   if (!isLemmy) return;

  // Create the navbar element
  const navbar = document.createElement('div');
  navbar.style.backgroundColor = '#FFF';
  navbar.style.color = '#000000';
  navbar.style.padding = '2.5px';
  navbar.style.textAlign = 'center';

  // Define the custom pages
  const customPages = [
    { title: 'My Profile', url: 'https://lemmy.world/u/0485919158191' },
    { title: 'c/sweden', url: 'https://lemmy.world/c/sweden' },
    { title: 'c/lemmyworld', url: 'https://lemmy.world/c/lemmyworld' },
    { title: 'c/plugins', url: 'https://lemmy.world/c/plugins@sh.itjust.works' },
  ];

  // Create links for each custom page
  customPages.forEach((page) => {
    const link = document.createElement('a');
    link.textContent = page.title;
    link.href = page.url;
    link.style.color = '#000000';
    link.style.marginRight = '10px';
    navbar.appendChild(link);
  });

  // Insert the navbar at the top of the document body
  document.body.insertBefore(navbar, document.body.firstChild);
})();