Change Screen Time Communication preferences on Mac
Use the Communication pane of Screen Time preferences to limit communication with others using phone calls, FaceTime, Messages and iCloud contacts. Communication to known emergency numbers is always allowed.
To change these preferences on your Mac, choose Apple menu > System Preferences, click Screen Time then select Communication in the sidebar.
Choose who your family member can communicate with during allowed screen time.
Contacts Only: Allow one-on-one and group conversations during screen time only with people in your family member’s contacts.
Contacts & Groups with at Least One Contact: During screen time, allow one-on-one conversations only with people in your family member’s contacts and allow group conversations that include at least one person in your family member’s contacts.
Everyone: Allow one-on-one and group conversations during screen time with anyone, including unknown numbers.
Allow contact editing
Select the “Allow contact editing” tick box to let your family member edit their contacts in the Contacts app. Leave it unselected to prevent them from editing their contacts.
During downtime, allow communication with
Choose who your family member can communicate with during downtime.
Specific Contacts: Allow one-on-one and group conversations during downtime only with specific people in your family member’s contacts. To specify the allowed contacts, click Edit, then use the Add or Remove buttons to modify the list.
Contacts Only: Allow one-on-one and group conversations during downtime only with people in your family member’s contacts.
Contacts & Groups with at Least One Contact: During downtime, allow one-on-one conversations only with people in your family member’s contacts and allow group conversations that include at least one person in your family member’s contacts.
Everyone: Allow one-on-one and group conversations during downtime with anyone, including unknown numbers.
Note: The available options vary, depending on the current settings for allowed communication during screen time.
Manage family member’s iCloud contacts
Set options for managing your family member’s iCloud contacts.
Set up iCloud contacts management: Click Turn On.
Manage a family member’s iCloud contacts: Click Edit, then view, edit, add or remove contacts.
You don’t see the Edit button until your family member accepts the request to manage their contacts. Until then, Pending is displayed.
Stop managing a family member’s iCloud contacts: Click Turn Off.
or Remove 
buttons to modify the list.