Member Notes for XenForo 2 allows your staff members to leave hidden notes on user's profiles.
Features:
Write notes on user profiles.
Viewing notes locked behind permission.
IP logging for notes is available.
Installation:
Extract the contents of the .zip file provided upon successful purchase.
Upload the contents of the 'upload' folder to your root XenForo directory.
Install the add-on through the XenForo Admin Control Panel.
Configure permissions in permissions area.