It is in the manual under server commands since g-code can not do this. And yes it is in 0.86.2 also you should upgrade to 0.86.3.
@autostart_next_job
Starts the next job in the print queue automatically as soon as the currently running job is completed.
Note: This is intended for printers that clear the bed automatically, because otherwise it will be printed on the full printing bed, which can cause damage!
@stop_next_autostart
Disables @autostart_next_job.