I put some pictures in the wrong library. How do I move them?

My question says it all. I can’t find a way to move images from one library to another. That’s all. There is no move option that I can find. I can delete, but it does not say what delete means as the warning just says it will be deleted. Deleted from my purchased list of photos? I don’t want that. Deleted from what Stock is showing me? I don’t want that either. The warning should say “removed from this library” if that’s what delete means.