You can now own multiple deck slots per Planeswalker! The multiple deck slots you can own should make playing in events a breeze - you can set a deck, then copy it for an event without having to rebuild it.
Multiple decks can be saved per Planeswalker to quicken your entry into events. You can buy two extra deck slots per Planeswalker. Each of these has a specific cost - one costs 200 Mana Crystals and the other costs 45000 Runes but requires the Planeswalker to be level 60. You can buy them in any order you choose, so you have full freedom with how you access them.