Plague Inc: Evolved

Plague Inc: Evolved

Bring your deadliest ideas to life
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Evolve a trait through Custom Event
So, I'm trying to make it so that a trait is only unlockable AFTER a certain date (Say 6 months after the game begins for simplicity.) Is there any way to do this through the custom events? Like, say, set a trait as a non-starting trait so it doesn't show up on it's own, then evolve it with the custom event once the time is right. Is this doable?