Equipment quoting prototype: what is missing from this workflow?

For people who prepare equipment quotes at small sales or installation businesses:

I’m building a small quoting prototype at AlphaLabs. It lets you choose a customer, add products from a shared catalog, adjust quantities and options, and prepare a customer-facing document for PDF or print.

This screenshot shows the customer-facing document preview and uses fictional companies, products and prices. This hasn’t been tested in a customer’s day-to-day workflow yet.

When a customer changes the products or quantities, what do you have to update manually before sending the revised quote? A recent example would be helpful. Is anything important missing or unclear in this preview? If your existing spreadsheet or software already handles this well, I’d like to hear that too.