Download current ChatGPT chat as markdown file. Just paste it into the dev tools console and it will download.

gistfile1.txt

// Inspired by https://www.reddit.com/r/ChatGPT/comments/zm237o/save_your_chatgpt_conversation_as_a_markdown_file/ + my own customisations

function h(html) { 
    return html.replace(/<p>/g, '\n\n').replace(/<\/p>/g, '').replace(/<b>/g, '**').replace(/<\/b>/g, '**').replace(/<i>/g, '_').replace(/<\/i>/g, '_').replace(/<code[^>]*>/g, (match) => { const lm = match.match(/class="[^"]*language-([^"]*)"/); return lm ? '\n```' + lm[1] + '\n' : '```'; }).replace(/<\/code[^>]*>/g, '```').replace(/<[^>]*>/g, '').replace(/Copy code/g, '').replace(/This content may violate our content policy. If you believe this to be in error, please submit your feedback — your input will aid our research in this area./g, '').trim(); 
} 

(() => { 
  const title = document.querySelector("a.dark\\:bg-gray-800 div")?.textContent || "Chat";
  const filename = `${title}.md`;
  let t = `# ${title}\n`;
  
  const e = document.querySelectorAll(".text-base");

    for(const s of e)
        s.querySelector(".whitespace-pre-wrap") && (t += `**${s.querySelector('img')?'You':'ChatGPT'}**: ${h(s.querySelector(".whitespace-pre-wrap").innerHTML)}\n\n`);

    const o = document.createElement("a");
    o.download = filename;
    o.href = URL.createObjectURL(new Blob([t]));
    o.style.display = "none";
    document.body.appendChild(o);
    o.click();
})();