Creating a Pop Up Window with a drop down menu


is it possible to create a pop up window with AppGyver? I would like the pop up window to open as soon as you open the page and have the page in the background blurred. In the pop up window I want to have a drop-down menu. I couldn’t really find a explanation on the Internet on how to create a pop up window in AppGyver. Or is there another term I should search for.

Thank you for your help!