I’m sure Charles will give you a more informed opinion, but my understanding is that long rooted veggies cannot be grown in modules, and that includes scorzonera. They send down long tap roots, and the module blocks the root. So sadly you need to sow in situ.
That said, I have experimented with carrots in deep modules, and this year I have some touchon carrots in 5″ deep modules. Scorzonera is very long, but I suppose you could grow one in a drain pipe filled with soil …
My problem is stony clay soil, and one apporach is to use a broken spade handle to make a deep hole, fill with compost, then plant the seed, thereby avoiding the root forking, and giving the veggy a good start in life.