The Scheduler will automatically run scheduled tasks at the time shown by the next run column - without your confirmation. However, if you do not want to wait for a task to be processed, you can start it any time using the Run command (Ctrl+R) from the Process menu.
You can stop a running task, scheduled or not any time by selecting it from the list and using the Stop command (Ctrl+S) from the Process menu.
Even though the Scheduler can run multiple tasks at the same time, unless you have a fast SCSI hard disk, you may want to schedule tasks to be run one at the time to make sure excessive disk usage does not slow down your computer too much. Or you can set the "Queue Overlapping Tasks" option from the General Preferences window to set scheduled tasks to be run one at the time.
[