How to implement Audio Unit that takes a sidechain bus?

Question

I am trying to implement an Effect Audio Unit (V3) that allows the user to use sidechain (take another track as input to modulate the effect). This, as I understand, is acheived by having two input busses. To keep it simple, I created a new Audio Unit Extension for Mac and I performed a minor modification to the boiler plate code that Xcode offered. That is, I added a second input bus called sideBus, following the same pattern as for inputBus:

@implementation exampleDSPKernelAdapter {
   exampleDSPKernel _kernel;
   BufferedInputBus _inputBus;
   BufferedInputBus _sideBus; // <-- added this extra bus
}

I then allocate this new bus in the init() method following the same pattern used for inputBus

- (instancetype)init {
   if (self = [super init]) {
       AVAudioFormat *format = [[AVAudioFormat alloc] initStandardFormatWithSampleRate:44100 channels:2];
       /.../
       _inputBus.init(format, 8);
       _sideBus.init(format, 8); // <-- added this initialization
       /.../
   }
   return self;
}

Allocate and deallocate resources in respective methods:

- (void)allocateRenderResources {
   _inputBus.allocateRenderResources(self.maximumFramesToRender);
   _sideBus.allocateRenderResources(self.maximumFramesToRender);
   /.../   
}

- (void)deallocateRenderResources {
   _inputBus.deallocateRenderResources();
   _sideBus.deallocateRenderResources();
}

Implemented the getter:

• (AUAudioUnitBus *)sideBus { return _sideBus.bus; }

And finally add the side bus to the list of input busses

- (void)setupAudioBuses {
   _inputBusArray  = [[AUAudioUnitBusArray alloc] initWithAudioUnit:self
                                                         busType:AUAudioUnitBusTypeInput
                                                          busses: @[_kernelAdapter.inputBus, _kernelAdapter.sideBus]];

   /.../
} 

However, when I load the AU on a track in Logic, it does not show the sidechain menu (see images below).

I am developing on Xcode 13.1, macOS 12.0.1.