As others have already mentioned, there is also a layout type for modal pop-ups. Also, check out this post on making the move to layout types and the features that help you with that:
I think you you need to set your layout type to Modal Pop-up
Remco was just ahead of me.
Since Mx 5.18, you can adjust the properties of the popup layout and specify what type of popup it should be. You could find more information in the reference guide.
If you have any questions, please let me know.