Looks like you can only queue one chest at a time. : r/ClashRoyale
Let us cancel unlocking chests : r/ClashRoyale
How to get chests faster in Clash Royale | 148Apps
i feel like this chest queue thing should be available to all players and should not be exclusive to pass royale players , it's more technical feature than a game feature. :
Chest Tracker for Clash Royale - Track Chest Cycle on the App Store