Add invoice & Estimate item lines that are 'inc.' included in the overall cost

I would like to add specific invoice & estimate items that are ‘included’ within the overall Invoice total. So it is showing at no cost or INC.
I have tried putting unit cost @ 0 but the line disappears in the invoice preview. This is useful in my field of architectural drawings where I can show the client item by item what is included in the overall package price. it would be useful be able to have the words INC in the total across from the line item.
Is this possible.
I have just started using Quick file & love it it is really going to benefit my new business.

Thanks for the suggestion, the lines will be stripped out if there is no value. You may want to consider entering any additional notes in the notes box line by line. They will then appear as follows in the invoice preview.