Computer Configuration > Administrative Templates > Microsoft Edge
Both
HKLM\Software\Policies\Microsoft\Edge
This policy controls the availability of the --ie-mode-file-url command line argument which is used to launch Microsoft Edge with a local file specified on the command line into Internet Explorer mode. This setting works in conjunction with: 'InternetExplorerIntegrationLevel' (Configure Internet Explorer integration) is set to 'IEMode'. If you set this policy to true, or don't configure it, the user is allowed to use the --ie-mode-file-url command line argument for launching local files in Internet Explorer mode. If you set this policy to false, the user isn't allowed to use the --ie-mode-file-url command line argument for launching local files in Internet Explorer mode. To learn more about Internet Explorer mode, see https://go.microsoft.com/fwlink/?linkid=2094210