If you would like to view your invoices in a certain order, Operate provides a feature that lets you arrange them according to your preferences. Operate can order your invoices based on the Product Group that the invoice has been issued for. 

To reorder your invoices, go to Settings > General > Customize > Invoices > Invoice Ordering. 

Now you can simply drag a product group to the desired position. The system will automatically save your change. 

Once your save your changes, your products/services will display on invoice lines according to how you have arranged them.