You can actually change the policy if you right click -> edit, the popup will show the policies. When you click save the change will be applied, you just can't see them. Alternatively, you can go to Security -> Access Controls, right click -> Update User Group on the user group whose access policy you wish to change and then change the policy in the "Context Access" tab. This screen shows the policies correctly and you can get the feedback that your change has been made.
