Auditing Changes to Enabled Features
The Enable Features page (Setup > Company > Enable Features) indicates which features are currently enabled for use in a NetSuite account. Even though there's no System Notes subtab, the page still supports system notes.
To track system notes for the Enable Features page, create a saved search and choose the Enable Feature filter for the Record Type field of the search. Run this search regularly to track changes to enabled features.
The Enable Features page includes a link to an Audit Trail page. You'll find it in the More list in the upper right of the page. See Auditing Account Preferences.