Computer Configuration > Administrative Templates > Microsoft Edge
Both
HKLM\Software\Policies\Microsoft\Edge
This policy lets you configure whether the history thumbnail feature collects and saves images for the sites you visit. When enabled, this feature makes it easier to identify sites when you hover over your history results. If you don't configure this policy, the thumbnail feature is turned on after a user visits the history hub twice in the past 7 days. If you enable this policy, the history thumbnail collects and saves images for visited sites. If you disable this policy, the history thumbnail doesn't collect and save images for visited sites. When the feature is disabled, existing images are deleted on a per user basis, and the feature no longer collects or saves images when a site is visited.