I need help making unique separate Einzatsgruppen ranks. Any tips on it?
If they were separated from the SS, the Einzatsgruppen would probably have some sort of official cover job so anything too overtly "death squad" is doubtful. One possibility would be to have them presented as a type of gendarmerie with a vaguely defined specialisation. In that case, their titles might be the same or similar to those of the army and their insignia, for example an "Oberleutnant der Einzatsgruppen" would wear 1 pip on a company officer epaulette.
If you want them to retain a connection with other NSDAP organisations, they might continue to wear collar insignia but in a different colour combination than the SS. for example, black bars, pips & leaves on a pale grey background. in term of titles, they would retain the "[name of grouping type]+führer" naming scheme but with different grouping names such as "bereich" or "Kontingent".
One last possibility is to give them a slightly innocuous appearance to partly disguise their actions by adopting a similar scheme to civilian organisations like the forestry service or postal service.
This would mean that the Einzatsgruppen soldier would equivalent of the following waffen-ss ranks would wear the following (obvious using different names):
Bewerber to Rottenführer: 0-4 silver pips in a row on a plain dark grey collar patch
Unterscharführer to Scharführer: 1-2 silver pips in a row on a dark grey collar patch with a thin pale grey edging
Oberscharführer to Sturmscharführer: 1-3 silver pips in a row on a dark grey collar patch with 2 thin pale grey edging
Untersturmführer to Hauptsturmführer 1-3 silver pips in a row on a dark grey collar patch with a wide silver braid edging
Sturmbannführer to Oberführer: 1-4 silver pips in a row on a dark grey collar patch with a wide silver braid edging, 2 of its corners being decorated by silver oak leaves
Brigadeführer to Oberst-Gruppenführer: 1-4 silver pips in a row on a dark grey collar patch with a wide silver braid edging, all 4 of its corners being decorated by silver oak leaves
Reichsführer-SS: 4 gold pips in a row on a dark grey collar patch with gold edging, all 4 of its corners being decorated by gold oak leaves