When I enable "Allow Purchasing of Assembly Items", NetSuite creates a new subtab on all Assembly Items called "Basic" with one field on it ("Preferred Vendor") and I can't move that field or subtab at all on the custom form. Can anyone else who uses this feature confirm if this is the same for them?

I have a subtab / "purchasing / inventory " with another sub tab called vendors. and the preferred vendor check box is inside that along with the vendor selection and purchase price

@Pete Kastner And that's on an Assembly/BOM record?

yes

Ahhh - when I turn on the "Multiple vendors" feature, then I also see what you see