Use Case: We use a shared responsibility model where some controls are provided by other parts of the org. Those controls are assessed separately and added to the evidence library for use in assessments of systems consuming the controls. My intent in changing the design and operating effectiveness is to add a value of "inherited control" that is treated the same as the "effective" value.
Currently, Modifying the Design and Operating effectiveness values is a customization as it impacts most of the key reports and dashboards for example:
Top 5 Org. by Control Test Results
Area of Compliance by Recent Control Test Results
Compliance Status by Regulation