Word for the act of disabling something
Solution 1:
You could consider using disabling as its noun.
Actual usage for iPad and iPhone:
For Disabling: Tap “Turn Off” to confirm disabling of the feature
Solution 2:
The noun form of disable is disablement. Note that gerunds can also be used as nouns if there's not a noun form of the verb.
All three of Confirm Disable, Confirm Disabling and Confirm Disablement would be understood. The last two sound better to me.
Solution 3:
"Confirm Disable," while not elegant would certainly be understood by your reader/user.