Official comment
Not hidden - if you use the LINK button at the top of the screen, that will enable or open the Ableton Link panel (depending on your setting in the preferences). To convert the Ableton signal to MIDI for the Groovebox, use this app on your iPhone or iPad, then connect the USB adapter and a USB cable to the Groovebox, set the Groovebox for MIDI-over-USB input, and you're golden.