[Terisa de morgan]

@eschwartz, yes, I could try to write the plugin but I'm afraid the effort (I would have to explore the way I should do it in calibre environment) doesn't worth the benefits I could get.

@BetterRed, it's easier. I only want to know if a book exists in any library according to the way calibre stores them, I don't need to search inside of opf files or to show all the libraries where it is. So, Explorer is find for it. And thank you, I'm going to search for the file explorers you mention.