In the "For invoicing" overview, start a new invoicing process with reported work that has not yet been included in any invoicing.
Click "Enter invoicing", but only save this invoice, do not issue it using the third invoicing step.
On the invoice overview then use the magnet icon on the far right to link this unissued invoice to an already issued invoice from the past.
Available invoices to link to the above will be offered to you.
Select the invoice and confirm by clicking the "Merge" button.
The final invoice will be the one you selected for the merge; it will contain the new statements and the amount will be increased by them, and the invoice from the first step will disappear after the merge.
You can now easily find this adjusted invoice by sorting the invoices by "Last modified".