Yes! You can fight a story boss in the main menu (fight icon) to unlock further levels. The next update will add a message to avoid confusion.
Ah, okay! I did see that button, but it wasn't clear what it was for. Clicking on it prompted me to choose a deck that I had won with, so I thought it was maybe a way to battle against my own decks or something.
Thank you for the feedback, gonna make it clearer!
