One big option for opening chests when all your slots are full other than salvaging chests should be to use gems to speed up a minion on a mission for the chest.
In the Chest Vault Menu
Click on a chest and its an option in a yellow box “Complete Mission”
Gem cost reduces with the time remaining
Madnezz119 is saying you should have the option to use Gems to complete a Minion’s mission while you’re on the screen for receiving another chest. Instead of spending Gems to open the newly obtained chest, you spend Gems to open the chest you’ve been working on.
In this scenario, you can’t move to the Chest Vault menu without salvaging the chest.
Right, Sure, should be able to do that - Good idea
Should also be able to click and see what the gear/item/spell/minion does when the chest opens