Complete creating the NEXT layout.. ONLY then, go to the next layout ?

I have a stage where I a SPAWNER object creating stuff on the layout from Left to Right (enemies, platforms etc..)

But even after the default C3 "loading" when starting, when I get to the layout it will show how the Spawner create things. (fast, but it's there)

Can I make in the layout before (loading layout or something) to make sure that it won't go to the next layout (stage creation) UNTIL it's finished creating it?

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Please explain step-by-step if possible, it will sure help a noob like me.

Thanks ahead!