title_body: How do I add an ISBN to Calibre ebook? According to the Calibre website:
  
  Click the book you want to edit and then click the Edit metadata button or press the E key. A dialog opens that allows you to edit all aspects of the metadata. It has various features to make editing faster and more efficient. A list of the commonly used tips:
  
  The ISBN box will have a red background if you enter an invalid ISBN. It will be green for valid ISBNs
  
  
  I see no ISBN box, red, green or otherwise in the edit metadata dialogue.
  On another Calibre page I see:
  
  you might want to display the ISBN, a field that calibre does not display.
  
  … followed by something about &quot;simply hover your mouse over the column header&quot; in the Calibre template language, which I cannot find.
  So, how do I add an ISBN (which I have) to the publication I need to convert to ebook?
upvoted_answer: The field for the ISBN is labeled "Ids:" and is located between "Tags" and "Dates". It allows you to enter ID types other than ISBNs.