How can I permanently change 'estimate' to 'quote?

Hello there, Smilingyellowvan.

When you create an estimate, you're giving your customer a quote or proposal for work that you plan to do. Which means an estimate and quote are treated the same in QuickBooks Online. For now, we're unable to permanently change it to quote.  

Although, you can create a custom estimate template, use quote as a header name, then download it. You can use this template when you provide a quote to your customer. I've got the article handy: Import custom form styles for invoices or estimates.

This is how it looks like:

I'll also share your concern to our management team. They'll submit this to our product developers for review, and it might be included in future updates. 

We'll be right here if you have more questions. Have a good day!