Under Management > Administration > Notification Content a number of variables ('Parameters') are available to be used in the body text of the email (header, task summary and footer). Unfortunately, the subject of the notification mails is always the same for a given notification type because the variable fields cannot be used.
Because of this, notification e-mails for a given notification type always look the same in the recipient's mailbox. It would be very useful, e.g., to be able to insert the current task step(s) in the subject of the 'task assigned' notification so the recipient can easily see what assignment(s) a notification mail is about.