mubi id.user.js

// ==UserScript==
// @name         MUBI id
// @namespace    https://mubi.com/
// @version      0.2
// @description  show mubi id in the interface
// @author       VDK
// @match        https://mubi.com/*
// @grant        none
// ==/UserScript==
function docReady(fn) {
    // see if DOM is already available
    if (document.readyState === "complete" || document.readyState === "interactive") {
        // call on next available tick
        setTimeout(fn, 1);
    } else {
        document.addEventListener("DOMContentLoaded", fn);
    }
}

(function() {
    'use strict';
   docReady(function() {
    var id = null;
    var json =JSON.parse( document.getElementById('__NEXT_DATA__').text);
    if (json['page'] == "/cast/[castSlug]"){
      id = json['props']["initialProps"]["pageProps"]["castMember"]['id'];
      document.getElementsByClassName('css-5s0yq')[0].appendChild(createLink(id, "li", "css-16o045c elv6jbt6"));
    }
    else if(json['page'] == "/films/[filmSlug]"){
      id = json['props']["initialProps"]["pageProps"]["film"]['id'];
      document.getElementsByClassName('css-1717uzm')[0].appendChild(createLink(id, "div", "css-1tzeee1 e1up1td00"));
    }
   });
})();



function createLink(id, element, class_name){
    element = document.createElement(element);
    element.setAttribute("class",class_name);
    var a = document.createElement("a");
    a.innerHTML = id;
    a.setAttribute("href", "#");
    a.setAttribute("class", "css-1s3qbnc");
    element.appendChild(a)
    return element;
}