Below is a working version modification of your code. Given the issues in your original code, I suggest that you spend some time reading the JSL documentation:
Help==>Books==>Scripting Guide
Also, in the code below, in your Save() function, you do not specify a path to where you want to save the data. You may need to specify a fully qualified path, in order to be able to save the table
dt = Open( "Data1.jmp", invisible );
tab = dt << Tabulate(
Add Table(
Column Table( Grouping Columns( :Code LLT ) ),
Row Table( Grouping Columns( :CodeTypePrmaryAndDesc 3, :CodeTypePrmaryAndDesc 4 ) )
)
);
dt_tab = tab << Make Into Data Table;
dt_tab << set name( "Tabulate" );
dt_tab << Save( "Data2.jmp" );
Jim