Hello there, lisa-purafog-com.

Currently, the ability to allow customers to accept estimates online is unavailable. I've got an option you may consider doing to get an online customer approval system set up for your Estimates in QBO.

QuickBooks Online has a lot of supported third-party apps that offer platforms for customer approving estimates. I encourage you to visit the QuickBooks App Center and search for a keyword like Estimates to get started. 

I am also including this article about customizing invoices, estimates, and sales receipts in Quickbooks Online for your future reference. It contains information about personalizing custom templates.

If you need further assistance, don't hesitate to ask. I'll be around to help you out.