In the latest version (22.1.6), there is new checkbox on invoices called Closed invoice.
When this checkbox is checked, invoice won’t appear in dropdown menus.
There is also a way to batch close (or open) invoices based on whether there is any balance due on invoice.
On Sales Invoices and Purchase Invoices screens, there is Batch Open or Close Invoices button.
This will display all invoices where balance due is zero and therefore could be marked as Closed Invoice.