Computer Configuration > Administrative Templates > Microsoft Edge > Performance
Both
HKLM\Software\Policies\Microsoft\Edge
Allows Microsoft Edge processes to start at OS sign-in and restart in background after the last browser window is closed. If Microsoft Edge is running in background mode, the browser might not close when the last window is closed and the browser won't be restarted in background when the window closes. See the 'BackgroundModeEnabled' (Continue running background apps after Microsoft Edge closes) policy for information about what happens after configuring Microsoft Edge background mode behavior. If you enable this policy, startup boost is turned on. If you disable this policy, startup boost is turned off. If you don't configure this policy, startup boost may initially be off or on. The user can configure its behavior in edge://settings/system. Learn more about startup boost: https://go.microsoft.com/fwlink/?linkid=2147018