How to add covers to books that don't have them?

[Siavahda]

Some books on my kindle don't have covers - they were transferred from one kindle to another (along with their sdr files etc) while both were plugged into my pc, so that I wouldn't lose my notes/highlights/reading place. So (if I'm using the terminology correctly) sideloading without Calibre.

The process worked fine to keep my notes etc, but for some reason the cover vanishes when it's done that way. I've attached a picture of how the book displays on my kindle. As best as I can tell, books like this don't have covers in the \system\thumbnails folder.

Does anyone have any ideas for attaching a cover to these ebooks? Yes, I could remove them and redownload them/sideload them with Calibre, but that means losing my notes and all, so I'd much rather not!

I've tried using Calibre's 'match book to library' function - since the book in Calibre has its cover - but that doesn't do anything. (In fairness, I think I misunderstood what the function is for.)

I've tried pasting the cover into the ebook's sdr file and restarting the kindle, but that had no effect either.

Tried saving the sdr folder, removing the ebook via calibre, sending the ebook to kindle via calibre, then pasting in the old sdr folder. (Just gave me a new copy of the ebook, with cover but without my notes.)

No idea what to try next! Suggestions?

[shamanNS]

You should also copy the whole "\system\thumbnails" from your Kindle A to your Kindle B.

[Siavahda]

I did that! But I've been sideloading this way for years, and the books missing covers - they're from way back before I knew to copy \system\thumbnails too. So the missing covers are not in \system\thumbnails, either in my most recent back-up or on my kindle. Sigh. That'd make it much easier!

[Siavahda]

A major solution to this issue is covered over in this thread, for anyone with a similar problem in the future.

The TL;DR version is, you need MobiMetaEditor, which you can find here.

MUCH THANKS TO shamanNS!

HOWEVER: I still have a handful of books without covers. Calibre says they have UUIDs, but MobiMetaEditor says they don't. Several books even have book covers in \system\thumbnails, but for some reason my kindle doesn't register their existence.

Help???