Holding in the Part button does... what?

[plofstof]

I saw a video on youtube that showed that, if you hold in the Part button while in Scene mode, the Part button starts blinking and the four Oscillator Level sliders turn into Part Level sliders. Other than a single reference in a random youtube video, I have not seen this functionality documented anywhere.

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.

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.

Is anyone else aware of this? What else happens if I hold in 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.

[Bizzaro]

Interesting feature. A shortcut to part mix would have been great...