We produce large product invoices as we are roofing merchants, usual size of 170 lines of stock. Currently the only way to save progress is to save which exits out of the invoice, then you have to find it, double click to open, move to the bottom of the invoice and continue.
As mentioned invoices with hundreds of lines need to be saved as worked on so that if something goes wrong, i.e. sage drive goes down or interrupted via phone etc.
So, save and continue button please.