Es gibt "jemandem wie ein Schatten folgen", but the meaning is a bit different: It means to always follow someone like a shadow follows a person, to always be in s.b.'s wake.
There's also "in jemandes Schatten stehen" which means "to be less important than s.b.", "to be in the background while this person gets all the attention", etc.
And just like there's "to follow in s.o.'s footsteps", there's "in jemandes Fußstapfen treten" which is closest in meaning to "to follow s.o.'s shadow"
I can't think of an idiom that's a direct equivalent.
So as always when translating something, you have to make a choice: Do you want to keep the image of a "shadow", and change the meaning slightly? Do you want to translate the meaning exactly, but change the image?