The short answer
Send a change order from the job. The customer approves it with a signature on their phone, and the approved amount adjusts the job total and rolls onto the invoice.
Mid-job scope changes are their own document, not an edit to the signed quote. You pull lines from your catalog, the customer gets a link, and they approve or decline with a signature.
An approved change order changes the job's total. The invoice reflects it, so the original quote, the change and the final bill all reconcile.
See it on your own quote.
Fourteen days, no credit card, your own price book. Send a real quote to a real customer during the trial.
or call/text (317) 850-1570