So your three buttons would send MIDI CC values something like 1, 64 and 127 (or whatever would trigger the three frequency values).
I don’t have any experience with the “assistant”, but you can certainly accomplish it with a script. I think you can do it with the Generic Remote as well.
I misread the OP and didn’t realize they’re asking for a single button to cycle different CC values.
I do not believe you can do this without a script unless you can control what the button is sending.
I totally understand
I’m not sure about the assistant, I somehow think that you would first have to transform your message by using an external utility, to simulate the functionality of a knob by using your button.
I have recently added a Korg Nano Kontrol2, and I am using it with all default CC mappings, but I have other controllers (Novation, Native Instruments or even synthesizers) on which I can program what the button send.
I wanted to use the Nano Kontrol to solve this : ) without studying more, but it seems that I have to experiment more with it (and install its drivers and software which have MANY MANY issues…)