User wants to create invoices from vendor bills and mark those bills as invoiced.
When you create vendor bills, CORE automatically creates time and expense entries linked to them. If you approve these entries from their respective screens, you can create invoices from them. You do not need to approve the vendor bill to invoice its items, but you do need to approve the expense entries that CORE created when you entered the vendor bill. Check out this article for details: Vendor bill not showing up in invoices. However, there is no option to mark a vendor bill as invoiced or billed. Instead, CORE marks the linked time and expenses as Billed when you invoice them.