I found a way to keep chests open lol

I'm the only one online

The chests close after you 'open' and close the chests but you can do it again to keep it open again.
You need 2 chests to get one chest to keep itself open
Open a chest and quickly click on another chest while the first chest is opening. Then the second chest should stay open. You can close out of the chest that is on your screen because that is the first chest.
This works best on touch-screen devices because you can click anywhere on screen. So you just have to have the chests on screen.
Me finding this was a completely accidental. Lol.