Editing layer 2 in SAMPLE EDIT > PROGRAM from the hardware?

So I have a pad with different sounds assigned to layer 1 and layer 2. I want to edit the 'pad start' and 'pad end' for each layer independently.

I can do that in PROGRAM EDIT (numerically). But I can also go to SAMPLE EDIT > PROGRAM and edit the pad start/end via the waveform - however I cannot find any way of selecting 'layer 2' this way. It always defaults to layer 1, even if I have tapped on and selected the layer 2 sample in program edit.

It sort of works in the computer GUI, sometimes, it's pretty buggy though, so perhaps it's not actually supposed to work at all?

Is this possible at all? Thank you!