I can't replace a comp on my timeline

I'm using after effects 23. I duplicated a comp in my timeline and then I'm trying to replace the duplicated comp with another comp from the project panel. But it's not allowing me to replace but it's suggesting me to place the comp at the top or bottom of the duplicated comp in my timeline. But in the tutorial I see it's possible to replace a comp with another comp.

So what's the problem or mistake happening by me here. Plz help me.

Thanks.