DefinePreferredLanguages
The value of
DefinePreferredLanguages influences the
Accept-Langague HTTP header.
It seems that this settings does not work well with q values (such as "en,en-US;q-09,.."), rather, it assigns q values.
With the following setting, the Accept-Language will be set to en,en-US;q=0.9,de;q=0.8,de-CH;q=0.7,de-DE;q=0.6:
set-itemProperty 'HKCU:\SOFTWARE\Policies\Microsoft\Edge' DefinePreferredLanguages 'en,en-US,de,de-CH,de-DE'