The command is quite useful, e.g. you can use it to set the library list for various projects that you are working on. Also, it can be used in batch job to do the very same thing.
on the command prompt and press [F4]. The command screen is shown. Enter the name and library of the job description who’s library list you want to set for the current job.
You can edit the library list for the current job, after it has been set, by replying *Yes to the Edit parameter.