I deal with this issue by loading my KEXT in a VM. I can then clear the approval state by rolling the VM back to an earlier snapshot.
If that doesn’t work for you — for example, if you’re working with a hardware-specific KEXT that can’t be loaded in a VM — then I recommend that you file a bug against TN2459 requesting that it describe how to do this on real hardware.
Please post your bug number, just for the record.
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Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware
let myEmail = "eskimo" + "1" + "@apple.com"