If you have multiple Wish Lists, then when you click to add a product to a Wish List, you will be prompted to choose which wish list you want to add it to.
Each list can have as many products as possible. Each list can have different products. They are completely separate from each other.
If you have added an item to your shopping cart and then decided you’d rather move it to your Wish List, you can easily move it from one to the other either by clicking the “Move to Wish List” button or the “Move to Wish List” text link.