How to get the total discount value, according to separate discount codes in the line level Details section's discount with the discount values in the Discount tab to a report?

There is a customized field named "New Discount Code" in the Details section of the invoice. There is a requirement to get the summation of this new "New Discount Code" discount amount with the Discount amount in the Discount tab to the Invoice report. Please check the attachments. Can I know if is it possible?

I have tried some ways by creating a sub-report. But the expected outcome was not coming. I joined the two tables as follows. Please check the below attachment.

And grouped by the [ARInvoiceDiscountDetail.DiscountID]. The output of the sub report as follows.

Left side of the report shows the discounts in the details section and right side shows the discounts in the discounts tab. But the discount named “SPRING” is missing in the above report. So can I know if is there another way to get the summation of these discounts into the report discount code vise separately?