Yes, you can create a single invoice in the New Invoice page. This page just gives you the option of creating either a single invoice or multiple invoices.
If you create a single invoice, it will be listed as a single invoice in the Invoice Management screen. Click on that single listed invoice, and you see the Invoice Details page.
If you create multiple invoices, it will be listed as an invoice batch in the Invoice Management screen. Click on that listed invoice batch, and you see the list of all the invoices that were created in that batch.