Up and down buttons: can they be accessed?

the cutie up and down buttons seem to change the octave of the MIDI note received. However, I do not see if they create a specific MIDI note or CC we can receive.

Can we receive the button event in the computer too? it would be cool for changing presets, etc.

Yes, the current octave will be sent over controller 16. Check MIDI 🎹 Events Documented or the patch pd_tickle_audio_midi_test.pd in the examples for a reference.

well for presets a range 0-7 looks limited, but I understand the original idea was octave transposition.
As we do not have any other button to change presets, it would be great (IMHO) a bigger range or maybe, more capacitive buttons on the surface.

If not a solution would be using two hexagons, one for preset up and another for preset down. Or an encoder with a color feedback…

I guess you could patch something using a rotary encoder. They are endless and the [chair.rotary-relative] abstraction can be used to access a range of your choice using [chair.rotary-limit-range]. You can give visual feedback using the LED colors.