You couldn't find that answer as FileMaker does not offer the option to set such properties for a drop down list or pop up menu.
Closest to that method that you might manage is to put a selection portal inside a popover. You can give the portal a scroll bar and specify the number of portal rows. you can set up the field or fields in the portal row as buttons that perform a script to enter the needed value into the field you would have otherwise set up with your value list. It's possible to set up the OnObjectEnter trigger on this field to open the popover.
You might be interested in the examples of using portals in place of value lists found in "Adventures In FileMaking #2 - Enhanced Value Selection".