I propose that the quick train feature be enhanced with the ability to replace the current troops and spells in queue. This feature would only affect queue troops, and not troops moved to camp.
Let me give the use case. I usually train a queue of donation troops. At some point I want to replace that queue with my next army before I attack. This is to prevent spillage of the random donation troops into camps, where I would have to waste them most likely. Pretty simple so far. The current process is to delete all the troops and spells in queue, and re-train the entire quick train army.
A replace option would keep any trained troops in the queue that match my new quick train army, deleted any trained or pending troops that don’t match, and add the remainder of troops from the quick train that are different.
So for example, let’s say I train six bowlers and a bunch of random troops in my donation queue. Now I want to replace the donations with an army. My army has 12 bowlers. So the replace feature would keep the six bowlers already trained and then queue up six more bowlers. In addition, the replace would delete the random troops from the queue (trained or otherwise) and add all the other troops to queue. Same for spells.
This feature would not reduce training time. It would give credit for training time already served, and make the quick train feature more convenient by eliminating the need to manually adjust between donations and armies.