Can you on a dual sabertooth motor control have two motors on the right side and two on the left?
Indeed, however as you might suspect, since it only has two channels, the two motors on the left will be fed with the same pulses, and same for the right side.
We use one dual motor controller on the Lynxmotion A4WD1 andA4WD3 robots given both motors on the left are the same, as are both on the right. This allows for skid steering.
If your motors are all different however, that can be problematic. Consider as well that each motor will need at most half the maximum current per side.
If you’re unsure, ask questions before wiring it up.