This version sets all of the checkboxes to checked, regardless of how many are in your list.
New Window( "Input Required", <<Modal,
V List Box(
align( "Center" ),
Text Box( "Set Preferences" ),
Pref = Check Box( {"Remove Single Value", "Remove Duplicates", "Group by Name"}),
Spacer Box( size( 200, 20 ) ),
H List Box(
Button Box( "OK",
RV = Pref << get( 1 );
RD = Pref << get( 2 );
GR = Pref << get( 3 );
),
Button Box( "Cancel", Stop() )
),
),
pref_list = pref << get items;
for (i = 1, i <= nitems(pref_list), i++,
pref << set(i, 1);
),
);