How to disable a Code in QS41

Hi
I want to disable a code in tcode QS41, but got the message that "Code 99 is being used and cannot be deleted".

The help message tells me that I can delete the code, if I set the "Inactive" indicator for logical deletion in customizing for catalog type But I want to keep the catalog type, and only inactivate the code.

I wonder if the code is in use, how can I see where the code is used?

If I delete the qode, what happens with the places where the code was used before deletion.

Would a solution be, to change the validity date for the code? (But "edit" ->"define validtiy" is greyed out).

Anyone who can  help me further, so I just can disable some codes.

Thanks,

/Lars