Native Instruments MASCHINE STUDIO Manual page 445

The pair of knobs for each Sound/Group allows you to quickly adjust the channel level and panoramic position.
For Sound slots, the knobs are visible only when the Pattern Editor is in Group mode. In
Keyboard mode, the knobs are not visible.
Configuring the Main Outputs of Sounds and Groups in Mix View
You can also easily configure the outputs of your Sounds and Groups in MASCHINE's Mixer:
Audio Routing, Remote Control, and Macro Controls
Audio Routing in MASCHINE
MASCHINE STUDIO - Manual - 445