How to save the result costume after a "paste on"

If i "paste on" spriteA on spriteB. After this, can i add the resulting image of spriteB into the costumes of spriteB?

Thank you, i didn't realize that "my costume" was actually the image of the costume currently displayed ...

I thought "my costume" and "item 1 of my costumes" (# 1 for example ...) were the same ...

Here is what I understand: "my costume" is in fact the image currently displayed on the screen of the sprite and not the image of the costume currently worn by the sprite (switch to costume (costume1) for example) ...

It's a perfectly good costume, even if it doesn't live in your wardrobe. The costume is what the sprite on the screen would look like if it were facing direction 90°. What MY COSTUME reports is the costume the sprite is wearing, whether or not that costume came from the sprite's wardrobe.