The image below will show how to achieve what you are requiring for a split board with 2 RCD's. The associated RCD at the top is the main switch, and you can enter something similar in the circuit designation to achieve a split board with the other RCD characteristics.

The Minor Works Certificate is based on the model in BS 7671, and only requires the details and test results of the modified circuit, not the associated switchgear. Hence, if the modified circuit is not an RCD or RCBO, then there is no requirement to test it.
I do understand what you are asking for here, and is a valid point, but is something that is specific to your scheme operator and not BS 7671. We may however look at including the provision in future versions of PIRform.
If you are concerned about not providing all the required information, then as long as the certificate complies to BS 7671 (which ours does) then you are also complying.