This isn't a game changing idea...But this will help a lot....
You have to attack soon but you have train the wrong troop. You have to train 6 archers but you forgot and train again to another barracks. That means you had train 12 archers instead of 6.
There should be a screen where you can see those queue troops.
Ex: Barrack 1 is training 2 dragons while barrack 2 is training 3 dragons. That means 5 dragons is queue overall.
The problem is...I don't have any Idea where to put it this screen... ???