[Pepin33]

Thanks for your answer, DotorOhh, but I think we are not talking about the same question.

I say that, at "Save to disk options", there are a "update metadata in saved copies" chekbox. If you check this, metadata from Calibre is saved inside the file of the book when saving (exporting) it. Including also the cover. Right. If you don't check this, then metadata are saved in another file. Right again.

But there is also another option, "save cover separately". If you check this, when saving a book, you get another file (jpg) containing Calibre's cover. But the cover inside the book format file is still updated with Calibre's cover. I think, if you're asking the program to save the cover separately, it must not be updated in the book format files...