Here is an annotated script that should help you understand the issue
Names Default To Here( 1 );
// Open sample data
dt = Open( "$SAMPLE_DATA/big class.jmp" );
// Create 2 journal windows, naming them what appears to be "Journal_1"
// and "Journal_2"
// Also assign the JSL variables j1 and j2 to the journals
j1 = New Window( "Journal_1", <<journal, dt << bivariate( x( :weight ), y( :height ) ) );
j2 = New Window( "Journal_2", <<journal, dt << oneway( x( :sex ), y( :weight ) ) );
// Create an empty journal window to move the other journals into
jFinal = New Window( "Final", <<journal );
// There are 2 methods below that can be used to append the journals to the
// final journal
// ^Journal pointer final^ << append( ^Journal pointer Journal_1^);
// jFinal << append( j1 );
// or
// window("final journal window name") << append( window("journal 1 window name"));
// window("Journal: Final") << append( window( "Journal: Journal_1"))
jFinal << append( j1 );
Window( "Journal: Final" ) << append( Window( "Journal: Journal_2" ) );
// The real name of the journal window is the key. Even though the code gives the name of
// the journal windows as "Journal_1", "Journal_2" and "Final", that is not the actual name.
// "Journal: Journal_1" etc. is the name. However, if one explictly assigns a name to
// journal, such as
// j1 << set window title( "Journal_1" );
// the window's name will be "Journal_1"
jFinal2 = New Window( "Final 2" );
jFinal2 << set window title( "Final 2" );
j1 << set window title( "Journal_1" );
j2 << set window title( "Journal_2" );
Window( "Final 2" ) << append( Window( "Journal_1" ) );
Window( "Final 2" ) << append( Window( "Journal_2" ) );
Jim