I can definitely help with making edits without sending it to your customer.
On the Create Invoice screen, you have the option to just Save rather than Save and Send the invoice. When you choose this option, your customers won't receive a notification every time a change is made.
Another suggestion is to leave the Customer email field blank.
This should get you on your way! Let me know how it goes or if you have any follow-up questions about invoicing in QuickBooks Online. I'll be here if you need further assistance. Take care!