If you ever need to query what reports are shared with a particular user(s) or group(s), you can query the sys_report_users_groups table.
instanceName.service-now.com/sys_report_users_groups_list.do
The table provides the following details:
- Report ID: references the report
- Group ID: references the group that the report is shared with.
- User ID: references the user that the report is shared with.

