CCN saves your library in plain text at:
"C:\Users\YourName\AppData\LocalLow\Ludosity\CardCityNights\Library.txt".
You can download and replace this file with my completed library:

mediafire(dot)com/file/2vtmywjhr9v4vqe/Library.txt


It contains 7 copies of each legendary and rare, 19 of each uncommon and 31 of each common card (so you can effectively use all 6 deck slots). Also included are the tutorial cards which are not available through normal gameplay.

CCN saves your decks in plain text at:
"C:\Users\YourName\AppData\LocalLow\Ludosity\CardCityNights\Deck_1.txt".
The number in the first paragraph of the file defines your deck logo while the second paragraph lists every single card by its respective number in the deck.

By editing this file you can bypass the ingame Deck Creator limitations (you can add all legendary cards to the same deck for example) as long as you have enough of said cards in the library.

You'll need to know which number represents which card though, see this guide: https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=229659417

Happy modding and let me know what crazy deck ideas you came up with!