I've been trying to figure out the same thing. I had some miles from the initial signup bonus, and was trying to extend their expiration. I found this Blog Post:
Rapid Travel Chai - You Have 5,000 Copa Miles Expiring Soon, What to Do?
I credited a recent Avis rental to Copa, but it hasn't posted yet.
I tried donating 500 miles, it posted to my account immediately, but it did not reset the expiration.
It is also unclear from the
T&C whether a transfer in from another account would count.
Would be curious about people's experiences. As this is a young program, the topic doesn't seem to be discussed much.