[BetterRed]

another arguably better idea than using a custom column - and it will work today - assumes you don't ordinarily have CBR comic book files - if you do then use one of the other Comic Book file types (cb7, cba, cbt, cbz)

Put the collection of covers you have for a book into rar file e.g. sunalsorises.rar, rename the file to sunalsorises.cbr

You can avoid the rename if you use WinRAR, it will allow the file extension to be overtyped when creating the file - ie you can overtype sunalsorises.rar with sunalsorises.cbr.

Add the sunalsorises.cbr file to the Sun Also Rises by Ernest Hemingway book in your library (drag/drop into Book Details will work)

If you check Preferences->Use internal viewer for CBR you can read the book with the calibre viewer.

But you may prefer to use a dedicated CBR viewer, I have a very simple one named CBR Reader, I'm sure there will be some better ones - see attachment

Doesn't do all you want, but it does at least get all the covers for a book into to the book folder in an accessible form

You can delete sunalsorises.cbr because its in your library

BR