How do I add a new sprite to an existing list?

On a tutorial, I am watching on making a memory card game it shows all the sprites on the same costume list but when I choose a new sprite it is shown alone. I don't know if I would have to redo the code for each new sprite or if the code would be carried over.

The code in a sprite applies for all the costumes in that sprite.

In the tutorial, I am using https://www.youtube.com/watch?v=51S28DEcr4Q it changes the costume to a new sprite but I am not able to do that is there a way that I can without copying the code to each sprite?

In scratch 2 all sprites are listed in the same costume list so the code can be shared without adding to individual sprites. Is there a way of doing this in scratch 3?