This is an interesting and complex change, wow! While I'm still getting used to it, some initial thoughts:
1. There should be a "Add a new row for this card" like feature that splits the row, i.e., subtract one from count of the existing row. That'd make it easier to associate cards in a deck with their respective collection copies when going from idea to built deck.
2. Exporting decklists should collapse multiple entries for a card into one. Judges don't care that some of my cards are EX, others are NM, it's not even reflected in the text export/decklist. This may have been a problem before but since I always use the same printing/language for a card in a deck, and didn't care about the selected condition (see also below), I may just never have noticed.
3. It is not possible to revert from a specific printing to the default one. It counts as a custom printing, including showing the yellow highlight. I have 17 Archaeomancers, and the row reverted to "default" claims that I don't have enough of the card in this specific printing, probably because all of them have set and language defined.
4. It would be nice to get back the red indicator for not owning enough of a card in any printing / all versions combined. That's different from having to improvise wrt printings to a significant enough degree to get a separate indicator IMO.
5. Language, set, version, all are more significant for deck building than condition, but it's still useful to track condition for cards when my expensive cards differ there. In particular for premodern or legacy decks I have old cards in multiple wildly different conditions, but otherwise (language, set) identical. Needing up to four rows to correctly reflect this in a built deck seems unnecessary, especially when I own exactly as many as I put in a deck. Perhaps the UI could be streamlined for this case, so internally it's still 4 entries/"rows", but it only shows as one, perhaps with a more complex Edition column?
