Find from here simple tutorial with the steps which guides you to delete a cron job in Windows Plesk Panel.
Step 1: If you want to delete a cron job or scheduled task, then just click on the checkboxof that specific scheduled task and click on the Remove button.
Step 2: Confirm your delete action by clicking on the Yes option in the confirmation pop-up.
Step 3: If you want to disable or suspend your scheduled task temporarily, then just uncheck the Active icon.
Step 4: You can also disable the cron or scheduled tasks by unchecking the Active check box.
Step 5: Again if you want to enable your scheduled task, just check the Active box.