Hi Frank,
You are right. If you change in CT04, this will impact all the class it is assigned.
Does your machine "Test" has a separate class ? Then you can do the same setting in CL02.
Select the charactericstic in CL02 & then click overwrite values & select "Entry required" check box.
The changes will be valid only for this class.
Regards,
Senthilkumar SD