Channel Mode and Link
Dual Channel, Matched Stereo, or Mono. One Switch.
Both channels get every control, independently, and a three-way Stereo/Mono/Dual switch plus a Link toggle take you from a dual channel setup, to a matched stereo pair, to mono. Dual channel makes things huge, it's perfect for 2-bus mixing but great for drums, bass, guitars, vocals, and more, it really sounds like the old units. Stereo gangs Channel 1's controls onto both sides for a matched pair, Mono sums to a single path for a source that needs to sit dead center.
Link works independently of the mode switch, engage it and Channel 1's controls drive Channel 2 directly, useful any time you want two sources handled identically without switching out of Dual mode.