Computer Configuration > Administrative Templates > Microsoft Edge
Both
HKLM\Software\Policies\Microsoft\Edge
OBSOLETE: This policy is obsolete and doesn't work after Microsoft Edge 102. If you enable this policy or leave it unset, the window.opener property is set to null unless the anchor specifies rel="opener". If you disable this policy, popups that target _blank are permitted to access (via JavaScript) the page that requested to open the popup.