Is there any way to set a cover for KUAL as it was in older versions?
cearp is working on it. See this post:
https://www.mobileread.com/forums/sh...31&postcount=6
Here you go!
Just a cheap and quick extension to set and unset the cover for KUAL.
As always, look through the shell script files and see what they're actually doing, use at your own risk.

Basically just copies this image (already in the zip) to /mnt/us/system/thumbnails/ and applies that thumbnail path to ALL of the records (you likely just have 1) that have files ending in .kual, in cc.db.

Reboots after the operation, to refresh the library to get the cover to show.
I'm sure there's a better way to do that that rebooting, so if anyone knows - tell me please!
It worked! Thank you!
Thanks cearp, works great!

Quick question: do you reckon this technique could be used to add a cover to any book, or is it just possible for KUAL?

I'm asking because since version 5.8.5, it hasn't been possible to have covers on AZW3 files downloaded through the Kindle cloud (the issue is summarized here). Several people (myself included) would be very interested in a way to bring back covers for those books!
Sure, the same idea could be used to apply/change the thumbnail for any book.

In the specific situation you mention, this is what I envision the steps would be for possible solution, in the form of a KUAL extension:

1. Query the cc.db to see which books are missing a thumbnail
2. Parse those files to get the ASIN (or did I see it in the cc.db for the file? - maybe)
3. Download the image for that ASIN, and that path to the thumbnail column for the book.

That would work well and not be so complicated for actual AZW files which have the ASIN present. If they don't, then we don't have so much to work with - unless the file is not drm protected, then we could extract the cover ourselves, but that would be more work.

Just to make it clear though, I won't develop this idea
making a little update
1)Upscaled KUAL image to 1012x1320
2)now scripts using thumbnail_kual_portrait.jpg from kualcoversetter folder(no more moving file in system/thumbnails/)

just put kualcoversetter folder to extensions
That’s great news! Unfortunately the ASIN actually gets overwritten with a random value in the process of uploading the book to the Kindle cloud, so I guess the covers would have to be extracted from the (DRM-free) AZW file. Would you have any pointers on how this can be done? There used to be a python script to do just that but it stopped working after fw 5.8.5, and as the developer dropped the project I always assumed it was no longer possible.

Yes of course, didn’t mean to imply that I was expecting you to implement it, sorry if it came through this way I was just curious if this could be an avenue for someone with development skills, time, and most importantly an interest in this issue to possibly explore. If there is a way to extract images from AZW files then I might give it a shot myself (although I’m not much of a developer so no promises ).
The ScreenSavers Hack has code to extract cover images from various book formats.
That script (ExtractCoverThumbs) can still do the job of extracting the cover and creating the thumbnail. So you would be left with "just" that final step of adding information into cc.db.

And unlike ScreenSaver hack's cover extracting code ExtractCoverThumbs correctly does its job for Calibre (& Amazon Previewer) generated KFX books