Does the A380 have more than one auto-brake disengage switch?
The A380 has one Takeoff Autobrake setting which is RTO and five Landing Autobrake settings which are BTV, LO, 2, 3 and HI. Some may read that as four plus the BTV, which is a variable deceleration compared to fixed deceleration. As you have noted, these are selected from the Autobrake selector switch.  

It is possible to disarm the Autobrake using a number of actions. One or two which have been mentioned already.


The Autobrake selector switch is set to Disarm.
The Brake pedals are depressed with a higher input than the Autobrake setting.  
The Spoilers are retracted.  
The Autothrust instinctive disconnect pushbutton switch is pressed. These are located at the ends of the Throttle control levers.  
The RTO Arm pushbutton switch is set.  


FCOM Reference for anyone interested - FCOM/DSC/32/10/30/20/00004244.0002001