For most us who don’t use TamperMonkey or GreaseMonkey, you can create a Bookmarklet that adds the excellent styleSheet listed above.
( See this Gist for an example usage: OpenAIPlaygroundShowPresets.js -- Bookmarklet to fix March 2024 CSS regressive bug (~"GM_addStyle" but without TamperMonkey or GreaseMonkey) · GitHub )
globalThis.GM_addStyle = globalThis.GM_addStyle || ( function(innerText) {
let doc = document;
let head = doc.head || doc.body;
let style=doc.createElement("style");
style.type="text/css";
style.innerText=innerText;
if(head) head.appendChild(style);
} );
GM_addStyle(`--the CSS
will go here--`);