Hi ogm148!
Hope you're having a good day! Let me share information about the estimate function in QuickBooks Online.
The option to create estimates is readily available in QuickBooks. There's no option to turn it on or off. If you want to create one, just click on +New and choose Estimate.
You can also check about creating and sending estimates for your additional reference.
Feel free to comment below if you need more assistance with creating estimates. I'll be glad to help you again.