Adding a simple html file (and its folder) as a book

Hi,

I'd like to add a simple html file and its folder to Calibre as I can do with other book formats and _without any_ additional manipulation/filtering/transformations/ etc Calibre normally does.
So clicking on it ,I can see it on my default browser or Calibre's browser.

I noticed instead that when I add a single html file, Calibre produces a zip file.
I could disable the plugin responsible for that. But still, Calibre rename the original html file, adding the author (that in my case is Unknown). In that case I cannot see it well on a browser.

Any idea how can I add a simple html file and its foder to Calibre?

Thank you