Thanks very much for the explanation. It totally makes sense now. With no indenting, I was destroying at the very time of creating.
So, may I ask, according to your experience, which way would be less likely to create incoherences for the future?
I have tried both ways you told me and after adding all the rest of the events, they behave correctly. So I don't know which road to take.
I am not using any IID for picking, so destroying the first instance does not make any difference, as the game runs as it should. But I might need to add some more loops to the sheet and still worried about how transitioning from and towards the layout would affect. I think this is due to my little understanding of loops and sub-events. That destroying event in the way you showed should be always the first thing to happen, no matter the rest of the event sheet, ain't it?
On the other hand, something on my mind keeps telling me that having the 'ghost' sprite on the unused layout could affect the sprite.count at some point, when adding more events that use that trigger (have already a boolean variable instance and a pick by comparison for that). I have lots of conditions like "when every instance is locked", "when there are no available instances left", "when every instance is on their variable position", ... some 'for each' loops,...
I'm trying to find on the web whether the triggers, loops, picks and counts takes into account every layout or not, with no result so far. Layers are mentioned everywhere, yet not layouts. Now reading about layouts to find out. Anyway, I guess by your words that it only checks active layout. So I would be worrying about nothing.
If only taken active layout, it seems a rather stable solution, since being static and not rendered, as opposed to having some rendered instances on start, which must be removed through an event storing/deleting data into memory, managing logic and checking triggers. But I could be wrong.
I am afraid to go on working in some fashion and then after a time realizing that will have to write back the entire event sheet because of the approach I had chosen was not right.
So, as a practical advise for a newbie- sprite on assets layout or destroying on start ???