Late 2019 I started to research the organization of an WWII Army Group of the German Army.
I was to busy last year... Let's try again. (Armies and Corps will follow)
The organizations varies greatly depending on period and region, anyway I took for sample the Army Group G late 44/early 45 at french/german border.
I start with the headquarters :
High command of an army group
Oberkommando einer Heeresgruppe K.St.N.9 (1.2.1943)
Chief Quartermaster Department
Oberquartiermeister Abteilung K.St.N.9a (1.9.1942)
Commandant of fortifications (higher command)
Kommandantur von Befestigungen (Höherer-Kommando) K.St.N.71 (25.11.1944)
Deputy General Command (HQ for conscription and local defense)
Stellvertretendes Generalkommando (wehrkrieskommando) K.St.N.5005 (1.12.1942)
For this one I'm just guessing, I'm not sure...
Branch office High Command of the Army
Aussenstelle Oberkommando des Heeres K.St.N.5015 (1.2.1945)
The two following was not exactly identified as part of HQ but can be assimilated:
Motorized Feldgendarmerie troop
Feldgendarmenrietrupp a (mot) K.St.N.2033a (1.11.1943)
Kartenbatterie K.St.N.2074 (21.7.1944)