Computer Configuration > Administrative Templates > Microsoft Edge
Both
HKLM\Software\Policies\Microsoft\Edge
This policy enables 'Save page as' functionality in Internet Explorer mode. Users can use this option to save the current page in the browser. When a user re-opens a saved page, it will be loaded in the default browser. If you enable this policy, the "Save page as" option will be clickable in "More tools". If you disable or don't configure this policy, users can't select the "Save page as" option in "More tools". Note: To make the "Ctrl+S" shortcut work, users must enable the Internet Explorer policy, 'Enable extended hot key in Internet Explorer mode'. To learn more about Internet Explorer mode, see https://go.microsoft.com/fwlink/?linkid=2094210