Where do you list subcontractor expenses for self-employment? Other articles say inventory but I think that is an old version of the app.

As per the T2125 Statement of Business or Professional Activities, Direct wage costs or subcontracts would go into the Inventory section. 

The inventory page only shows up in the Self-Employment section if you choose the "business" type and say Yes to the question "Did you sell products that you bought or manufactured".