the only one extension of such type which works

Extension does what it purports to, but that's it; the output doesn't really look as good as the original GPT conversation, and it does not export the whole conversation tree (so, if you have response edits or you re-ran one of the prompts, you can't switch between them). The extension is still useful, I suppose, but if that's all you want, I recommend the extension called "SingleFile." It will export whatever branch of the conversation *exactly* as it is rendered to you.