Native sidechain in Logic?

We've been developing a sidechaining plugin (stereo in/out, with stereo SC) but cannot figure out how to add a sidechain dropdown in Logic. For example, see the "Side Chain" option in the upper right of this compressor:

We have gotten sidechaining to work without a hitch in other DAWs... but it seems Logic might require some kind of workaround? Any advice appreciated. Thanks!

Have you looked at the NoiseGate example in JUCE/examples/PlugInSamples/NoiseGate? It adds a sidechain bus (and the dropdown menu) and works fine in Logic. Also check out this guide.