Three ways:
- Quick Start: setting up the new iPhone from the old one brings RectoVerso’s library with it.
- An iPhone backup: restoring one from iCloud or a computer does the same.
- A library backup: on the old iPhone, use ⋯ › Settings › Back up library… and send the file to the new one (AirDrop, or Files). There, install RectoVerso and open the file with it.
A library backup is also the way to move only RectoVerso, or to merge two phones’ decks with Add its decks.