The MakeBelly command corresponds to the options on the Belly tab. It is used for both bipeds and quadrupeds.
To automatically create the belly controls, the command requires two guide objects that define its lower and upper extremities. You have control over the belly slide. The belly is parented to both the hip (MakeHip) and vertebra objects.
Example of a belly rig attached to a hip icon. As the hip rotates, the belly follows.