Computer Configuration > Administrative Templates > Microsoft Edge
Both
HKLM\Software\Policies\Microsoft\Edge
Define a list of sites, based on URL, that are forced to be shown in sidebar. If you don't configure this policy, no app is forced to be shown in sidebar. If the 'HubsSidebarEnabled' (Show Hubs Sidebar) policy is disabled, this list isn't used and no sidebar can be shown. For detailed information about valid url, see https://go.microsoft.com/fwlink/?linkid=2281313. Note: URL patterns are not supported in this policy. You should provide the exact URL of the app. Example value: https://www.contoso.com