Once you open a crate, you can put any other crate into the queue by tapping on the crate and tapping the ‘Queue up for auto-unlock’ button. The selected crate will start opening once the timer for the currently opened crate runs down without any more interaction or being online.

To remove a crate from the queue tap the crate and then tap the ‘Remove from queue’ button on the information popup.

It is possible to put multiple crates in the queue. If multiple crates are in the queue for auto-unlock, they will be opened one by one in the order that they got queued.