The only documented reference I can find to holding in the Part button is the Version 1.20 (March 2020) patch notes suggesting that holding in the Part button will lock the panel.
Is anyone else aware of this? What else happens if I hold in the Part button?A key lock function has been added to the [PART] button.
Pressing and holding the [PART] button makes the button flash and engages Key Locking.
The operation while pressing the [PART] button can be operated by releasing the [PART] button.
So if I hold in the Part button it does flash, but I don't think it locks the panel. It definitely does not lock the Oscillator level sliders, and changes their function from Oscillator levels to Part levels...
If anyone can find the Part Level functionality documented somewhere I would really appreciate a pointer to the source.