Thanks Audrey and Bruno for responding but I'm afraid that there is no solution.

Audrey:
Suggestion 1: There is no filteroption in expand mode to exclude separate sound setting.
Suggestion 2: To my opinion the seperate sound setting (page 159 of manual) is part of the current panel setting which can only be saved by saving current panel.
Current panel can be excluded from loading from/saving to disc or SD but other settings, like split point, equalizer, and many other are than excluded as well. So this is no option.

Bruno: to my opinion this has nothing to do with midi settgings.

I'm afraid that I have to live with it. I will have to do this setting everytime I want it or resave every file with my preferred setting.
Maybe Alec/Technics player (the expert on KN7) can confirm this?