I know there is a dedicated socket for the Expression Pedal because I use one all the time so at first I thought you could be confusing this with the optional Organ footpedal board outlet. However, I've just looked in the KN7 Manual, page 200 and it says (and I quote):-

SUB OUT
The sounds from desired parts can be output independently from those terminals. (Refer to page 161).

On looking at page 161, under 'SEPARATE SETTING' there is a full explanation of how to use this SUB OUT facility. Hope this helps.

You raised a very interesting query and I was curious to know what the answer could be hence the reason I looked in the Manual.

Thank you for that, you learn something new every day don't you?

Regards,

Aud (U.K.)