As of right now, you need to call them. The "Reservation Portal" is only for rescheduling.
When KI first opened their reservations, I accidentally booked the wrong day and the change-online system didn't exist yet so I had to call in to cancel. Aside from the maybe 30 minutes on hold to be able to talk to someone, I had no issues.
Total Coasters: 150(!)
Top 10 Steel: Maverick, Skyrush, Intimidator 305, Fury 325, Banshee, Millennium Force, Raptor, Superman: The Ride (SFNE), Top Thrill Dragster, Big Bad Wolf
Top 10 Wood: The Beast, El Toro, Phoenix (Knoebels), Boulder Dash, Thunderbolt (KW), Mystic Timbers, Comet (Hershey), Hercules, Shivering Timbers, Jack Rabbit (KW)
Top 5 Hybrid: Twisted Timbers, Steel Vengeance, Goliath (SFGAm), Wicked Cyclone, Great White