I've got your back, @moonvalley.

In QuickBooks Desktop (QBDT), you can add another column on your invoice to enter the amount for the discounted items. However, you'll have to input the amount manually. Here's how:

1. Go to the Lists menu, then select Templates.
2. Open the invoice template you use when creating invoices.
3. In the Basic Customization window, click the Additional Customization.
4. Go to the Columns tab, put a checkmark in the Other 1 and enter the title of the column ("Discount column" or "Discounted amount").
5. Click OK twice to save the customization.

Once done, you can now create an invoice and enter the discounted amount of the items selected.

I know that you are looking for a way to automatically enter the amount of the discounted items. But as stated by my peers above, the Other columns on the invoice template is just a custom field. Thus, you'll have to manually enter any information you want to be added to the invoice.

You might want to check out this article to learn more about customizing form templates in QuickBooks Desktop: Use and customize form templates. Please know that this article is for the US version but this also applies to other regions.

Please let me know if you need clarification about this, or there's anything else I can do for you. I'll be standing by for your response. Have a great day.