Hi Veltsu,
I'm not sure why you refer to your foot controller as a "midi" controller because foot controllers are just switches used to enable or disable (turn on or off) the various functions of a keyboard e.g., pads, panel memories, panel memory banks, sustain, fills, start/stop, and so on. I have never had the opportunity to look at a KN2600 but I suspect it is designed and engineered like all other Technics keyboards, therefore has a foot controller function that is common and works exactly as the others do.
Somewhere on your KN2600 will be a button labelled "Program Menus" or some similar meaning name. Press it and look for a "Control" menu. Press that button. The Control Menu will appear and allow you to program foot controllers and/or an expression pedal.
Your manual should contain a section devoted to Program Menus and their options/functions.
As I said above, foot controllers are unrelated to midi. You cannot change midi channels with a foot controller if that is what you're thinking.
Hope this helps.
Best Wishes, Chuck