User Configuration > Administrative Templates > Microsoft Office 2016 > Security Settings > Trust Center > Trusted Catalogs
User
HKCU\software\policies\microsoft\office\16.0\wef\trustedcatalogs\catalogfsdefault
This policy setting allows you to set the location of the Shared Folder Catalog that is designated as Default. The web add-ins contained in the Default Catalog can be inserted into Office documents by users. If the policy setting that allows users to control the Trusted Shared Folder Catalogs is enabled, this setting will be ignored. If you enable this policy setting and do not enable the policy setting that allows users to control the Trusted Shared Folder Catalogs, you can set the URL for the Shared Folder from which users can insert web add-ins into their Office documents. If you disable this policy setting and do not enable the policy setting that allows users to control the Trusted Shared Folder Catalogs, users cannot insert web add-ins from a Shared Folder. If you do not configure this policy or any other policy settings in the Trusted Catalogs folder, users can set their own Default Shared Folder location.