To do so you simply add the staff you wish to be sickness managers into a group, and then assign that group to all of the staff you wish to have the group manage for. Admins and managers are still notified and can still book and manage sickness if they wish.
Here's how you do it...
Firstly, go to your Staff Directory and select the members of staff you wish to be able to manage sickness and click on Add to group
Give a name to the group and click on Save
Go back to your Staff Directory and choose the member of staff you wish to add the sickness managers to and click on their Settings tab. Under staff groups that can manage Sally's sickness you can check the box of the name of the group you want to be able to manage that staff member's sickness
Now the people in the group you have created will be able to manage sicknesses for all staff that their group has been set as sickness managers for. Managers and Admins will still be able to manage sickness as well, though if a manager or admin does not want to receive sickness notifications they can go to the Settings
tab in their profile and filter the notifications they would like to receive, please note that these notification settings also apply to holiday notification