Customizing the metamodel > What you can do with USRPROPS/SAPROPS > Layout capabilities > Grids, list boxes, and text boxes > Defining a LIST of values > Checkboxes versus dropdown list
  
Checkboxes versus dropdown list
If the number of values in the LIST statement is four or less, System Architect displays it as a list of checkbox choices.
If the number of values is five or more, it displays the list as a dropdown list. Users can type in their own value in a dropdown list box. If you want a dropdown list box, but have only four or less LIST values, use the LISTONLYCOMBO keyword.
See also
Defining a LIST of values