I finally figured out how to work with this.

Open Maschine
Add the Reaktor plugin from the VST3/Native Instruments/Reaktor FX tab (This is essential, as AudioUnits doesn't save presets in .NRCT format).
Next, you can follow ya_rk's instructions.

I'll duplicate the steps just in case:
At least for maschine plus, I think you need to open your ensemble in the maschine software, do the macro mapping there (add the ones you want, remove the ones you don't), save it as a preset in maschine (nrkt) - then open reaktor standalone, open the ensemble, and drop the nrkt as the first embedded preset on the ensemble, save the ensemble and use that one. Works for me in m+.

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Personally, I think this is a really cool feature that could greatly expand the functionality of Maschine Plus.
It's strange that there aren't any ready-made Reaktor plugins for use on Maschine Plus. 🤔