Temporary solution for https://discuss.google.dev/t/191869

looker_studio_firefox_nav_fix.user.js

// ==UserScript==
// @name         Looker Studio Firefox Navigation Fix
// @namespace    https://pjpscriv.com/
// @version      2025-08-26
// @description  Fix the (insane) issue that Looker Studio's navigation is broken in Firefox
// @author       @pjpscriv
// @match        https://lookerstudio.google.com/*
// @icon         https://www.gstatic.com/analytics-lego/svg/ic_looker_studio.svg
// @grant        none
// ==/UserScript==

(function() {
    'use strict';

    const intervalId = setInterval(() => {
        const nav = document.querySelector('.top-page-navigation');
        if (nav) {
            nav.setAttribute('style', 'top: 36px;');
            console.log('[USERSCRIPT] Applied Looker Studio Firefox Navigation Fix');
            clearInterval(intervalId);
        }
    }, 50);
})();