User Configuration > Administrative Templates > Microsoft Word 2016 > Word Options > General
User
HKCU\software\policies\microsoft\office\16.0\word\options
This policy setting configures the "Startup Boost" checkbox found under File tab | Options | General. Startup Boost improves Word's boot time by prewarming the app on user login. If you enable or do not configure this policy, users will be able to use the Startup Boost feature. The Startup Boost checkbox will be enabled and checked by default. If you disable this policy setting, the Startup Boost feature will not be available. The Startup Boost checkbox will be disabled and unchecked. Note: This policy setting only applies to subscription versions of Office, such as Microsoft 365 Apps for enterprise.