This feature looks really good and I'm glad I can finally uninstall the extension :-D It works really well for almost all of the kingdoms.
There is still one place where it is a little weird, though. For split piles (Encampment/Plunder, Patrician/Emporium, Catapult/Rocks, Settlers/Bustling Village, Gladiator/Fortune, Sauna/Avanto), both of the cards in the pile appear in-line with the supply cards, meaning that it looks like there are 11 or more cards in the supply. This causes there to be more than two rows, and then there ends up being a row on top with just one card on it.
The point of this feature is to be able to display all of the cards on-screen that are in the kingdom, this is a lot less effective when there are more than just the two rows of five cards visible. With the only exception being Young Witch, the main ten kingdom cards should just be displayed before anything else at all.
Page, Peasant, Knights, and Castles work beautifully. The interface for any of these would work just fine for the split piles. It could just show the top card of the pile in the two main rows and then have the bottom card appear below, or it could show the randomizer card in the two main rows and show the individual cards below.
This feature is really important and I'm glad it was integrated into the main client -- I don't know of any other tool for visualizing kingdoms at all that exists anywhere (and has all cards from all expansions), and I use kingdom visualizers at least one a week consistently (not even including all the times where this is useful to have up when broadcasting games). Having two rows that just tell you what kingdom cards are in the pile is the heart of this feature, so having it work for split piles would make this feature complete.