User Configuration > Administrative Templates > Microsoft Office 2016 > Miscellaneous
User
HKCU\software\policies\microsoft\office\16.0\common\general
This policy setting controls whether users can use the Writing Assistant feature. If you enable or don’t configure this policy setting, users will be allowed to use Writing Assistant and it will be enabled by default (unless the users disabled it). If you disable this policy setting, users won't see Writing Assistant by default. Note: This policy setting only applies to subscription versions of Office, such as Microsoft 365 Apps for Enterprise.