When editing a response policy, you have the option to remove feeds from the policy. If you do this, you can split the modification into a new policy and leave the existing policy as it was.
For this option to be enabled, feeds need to be removed from the the policy in the Edit policy dialog. Then, check the Leave removed feeds as a separate policy instead of deleting them.
The removed feeds, as well as any other changes to the policy will be split from the policy and become a new policy. The remainder of the original policy is left unchanged.