I created hundreds.
First, I want to try. Then I decide, how to use. But now I can not try.
I want to insert here a picture - no way directly from PC...
Edit, later
OK, understood. I HAD already user categories, but all of them was created from other fields. Nowhere is written, that this is not acceptable.
About Calibre: when I click on USER categories, why pops up a panel with all OTHER things, absolutly not related with USER categories? ... And so on.
Calibre's only pro: nothing else is... Earlier I was waiting 5 years (till now) for the first, elementary thing: hierarchical categories (
https://www.mobileread.com/forums/sho...d.php?t=108794)
About plugin: it's good, I shall use it. Thank you for your work and help.