Hello, I am a SAS employee and thought I would help with the questions of "How do you know the "group columns()" statement?". I can think of two good ways to find the JSL command to group columns or perform other actions.
1. Look under help->Books->JSL Scripting Guide, then in the pdf file search for Group Columns.
2. If you look in JMP under the help->Indexes->Object Scripting menu, you can then select Data Table Cols. This will then show all the messages that the column object can take. Group Columns is one of the messages shown.