Remove an item category option from particular sales order type

Hello,

I am trying to exclude one item category option from particular sales order type.

The sales order type is Stock order (ZSK1).

In line items, I am trying to remove one of the options within the item category. When I expand item category option, I see stock (ZINK) and drop ship (ZDRP) item category options. I want to remove the drop ship (ZDRP) item category option.

How do I remove this option from item category selection for this particular sales order type?

I would greatly appreciate your help.

Thanks,

Kumar