Kan as blackhornet said you don't need to destroy them if there on another layout . We are telling you that because normally the reason people what to destroy an object at start of layout its because they want to spawn it later . so what we are saying is if that's why you need the feature just don't put the object on the layout make a blank one instead and put the objects there then you just tell C2 to spawn the object whenever you need it without having to destroy it . This is the main way of spawning object so you don't need to destroy unwanted instances . Also to Spawn something in Construct 2 it just has to exist somewhere in your project
if this is not the reason you need to destroy on start of layout tell us but this is the reason most ask
so im not really understanding how ether method would not work for you in fact its better