Well, what's about speech recognition then?
Touch keypad is a key away from any output value (U, I, P) what can be set:
I suppose that having multiple input devices should simplify and speed up entering desired values. Two encoders on Keysight could serve changing simultaneously two values in case that two hands are used, and if operator have a good bi- or multi-tasking perception. For the rest of the people and situations one hand will be involved anyway, and don't know what is a real advantage.
In our "single hand" case moving from one output value to another is again a single touch operation..., and if encoder is used to set voltage on Ch1, with one touch to e.g. current of Ch2 you can continue to make adjustment with encoder. Additionally, "user sw" can be used to set encoder step (e.g. Auto, 100 mV, 500 mV, 1 V, 2 V or 5 V) that further simplify and speed up settings.
Regarding external keypad: yes, it can be supported in firmware (we have a complete control of it
): it can be seen as an USB device, or another possibility is to use UART interface that is exposed on the front panel.