Thanks guys that helped indeed. 
Only thing I don´t understand is the changing Patch on the Global MIDI channel you mentioned or if that is actually a problem for me?
Just to be clear this would be my plan of the OT(octatrack) sequencing the Snow:
Let´s say in Multi-Mode with enabled switching Multis with Program Change messages in the Config Menu:
OT´s Midi Track 1 sequencing Part 1 on Midi Ch 11 = Global Channel of the Snow
OT´s Midi Track 2 sequencing Part 2 on Midi Ch 12
OT´s Midi Track 3 sequencing Part 3 on Midi Ch 13
OT´s Midi Track 4 sequencing Part 4 on Midi Ch 14
so if I want to change the Multi for another Pattern from the OT it has to send a Program Change message only on the Global Channel (Ch 11)
in order to change the Complete Multi with all 4 Parts and the same time, meaning Part 1 (Global Channel) would change the sound as saved to the according Multi?
If it´s like that it would be nice.
Or will it be like that?
In order to change from one to another of the 64 Multis via Programm Change messages Part 1 of the Multi always has to be one of the first 64 Patches (from all the 1024 patches of the Snow),
as the multi selection responds / corresponds to the patch selection (in Single Mode?) like flabberbob mentioned? 
Sure I´lll purchase it anyway as the size and weight of the Snow is just right for lugging around and doing live gigs.
Thanks!