Can you try clearing your browser's cache and reloading the page? I'm unable to reproduce this issue; the code editor works fine for me.
As an aside, we're deprecating the code editor feature and won't be replacing it when the old dev tools are eventually removed. We recommend that you use any code editor you like instead. One such option for web-based code editing is https://codepen.io/.
I made the mistake of not trying from another machine. It appears this is related to some kind of inherited browser policy preventing this from working and the others I had test would have had the same policy issue. It is working from my personal laptop just fine.
That's very unfortunate to hear though, as using the code editor allows you to use your credentials without setting up any auth.