Hello Claus/ Jasmine,
Hope you guys are doing good !
If I understood the requirement clearly the Claus want to change rate type,
I believe change should be done on below path
TRM-TM-General Settings- Organization - Define calculation indicator.
Once we define the same and assign the same into define company code additional data system will pick the same for TBB1.
Let me know if you have any further question.
Regards,
Jain