I'm currently working on a small shop inside a website.
To keep the shop simple and clean there will open a pop-up when the user adds a product to their cart (to specify the product). The thing is that with some elements I need a second pop-up or a notification where the user can also customize things in. (Like downloading a template.)
To get a good ux I don't want a pop-up in a pop-up, a regular pop-up is not a option because they need to be interactive.