The Pokémon TCG Card Dex allows players to scan cards and document their card collections, supporting all cards released since the launch of the Sun & Moon Series. Cards are sorted by expansion, and can be filtered within each of the expansions by card type. A scan feature allows the user to use the phone or tablet's camera to scan a physical card and mark it as owned within the app. With the sunsetting of this app, it appears that all of user's collection data will be permanently lost. Unfortunately, it seems that users will also not be able to export these collections in any format.
The official Sunset Information FAQ has stated that the app is being discontinued in order for The Pokémon Company to dedicate more resources towards ongoing development of the Pokémon TCG Live software.