Computer Configuration > Administrative Templates > Microsoft Edge > Application Guard settings
Both
HKLM\Software\Policies\Microsoft\Edge
This policy allows Microsoft Edge computers/devices that have application guard enabled to sync favorites from the host to the container so the favorites match. If 'ManagedFavorites' (Configure favorites) are configured, those favorites will also be synced to the container. If you enable this policy, editing favorites in the container is disabled. So, the add favorites and add favorites folder buttons will be blurred out in the UI of the container browser. If you disable or don't configure this policy, favorites on the host will not be shared to the container.