Simply, a report that looks at TOTAL inventory of a sku, Deduct the demand and anything at a NEGATIVE will show up on this report, showing the numbers that it was oversold.
This could be a report in insights or a filter or tab in products. (as long as an export is possible)
This is helpful to know what products need immediate reconcile of inventory. At our company, we print products on DEMAND, thus we would use it as a "production" list.
below is a screen grab from another shipping site that has it, We personally love shipstation...and would rather this feature be added then change to the other system.