Quantity pending fulfillment (not yet shipped) is the difference between Quantity and Quantity Fulfilled. This information is not exposed to the transaction. Users may create a custom field and use a formula to get the desired result.
1. Navigate to Customization > Lists, Records, & Fields > Transaction Line Fields > New.
2. Enter a value for the Label field.
3. Set Type to Free-Form Text.
4. Uncheck the Store Value checkbox.
5. Under Applies To tab, put a checkmark for Sale Item.
6. Under Validation & Defaulting tab, enter this formula on the Default Value field:
7.Mark the Formula checkbox.
8. Click Save.