Hello there, @GenTent. I'm happy to provide you with some information that will help you with your concern.

Yes, you can override the customer's email address when you want to send batch invoices. You'll just have to change it directly in the customer's profile before sending the batch invoices.

Here's how:
 

1. Go to the Sales menu and select Customers.
2. Click on the specific customer you want to change the email to view their customer details profile.
3. From the Customer details page, click the Edit icon to change the email address.
4. Then select Save.
    

Then if you want to override the "from" email when you send an invoice, It is impossible to do so, but you can add a Gmail address if you have one.

Here's how:
 

1. Create an invoice or open an existing one.
2. Once you fill out the necessary fields, select Save and send to open the preview window.
3. Above the customer’s email, select the From dropdown.
4. Select Add Gmail address, then Connect Google account.
5. Enter your Gmail address and your Gmail password, then select Next.
6. Select Allow.
    

You can refer to this article, for additional details: Use your Gmail address to send invoices.

I've also added this article for future reference: Customize invoices, estimates, and sales receipts in QuickBooks Online.

If you need anything else, especially when you want to manage your sales forms, I'll be around. Stay safe and hydrated!