Hello,
The attached mod/spl file will add the functionality to track who is changing Group Membership and the Notify/Manager flags on the grpmem object. When a user is added/removed from a Group or has their Notify/Manager flag changed they will have an activity written to their Activity Log. Note, this code has only received minimal testing and is not supported by CA. Use at your own risk!
Follow these steps to implement this customization.
Group Changes
Group Flag Changes
Hopefully someone finds this code useful! Let me know if you have any questions.