Add line items to Draft Invoices

As an Auditorium Manager I would like to be able to edit a Draft Invoice by adding additional charges under the specific date and space on the invoice if I failed to add the charge on the cost tab prior to creating the draft invoice. Currenty, if I miss adding a charge. I either have to add it like a note on the invoice or I have to delete the invoice and create another one.
I have a group who are booking multipule sapces for multipule days with different hours. We have additional fees for Site-Supervisors, Technicians, Custodian but those only occure for the day not for every space. I choose the main location and added the additional charges for the three dates. However, I missed the Site-supervisor charge on one date. After creating the draft invoice. I could not go back into the COST tab to add the additional charge and I could not add the additional line under the day that was missing the charge. 

Add check boxes to Invoice Edit option so that you can select and modify more than one line at the time.