I found out something very important:

One thing excellent about Sk880/WK8.. series is the fact that you have 4 analog outputs named: left, right, out1, out2.

Basically each track can send its output to one of the following configuration:

1) stereo: Left + right
2) stereo: out1 + out2
3) mono: out1
4) mono: out2

Here are some of my observations and I appreciate any comments about these:

a) there is no mono: left or mono: right

b) does "stereo: left + right" sounds the same as "stereo: out1 +out2"?

c) that one is very important: metronome tone only comes from "left + right", there is no way on earth to make it come from out1 or out2 or both. Any trick?

Thanks