It's not a setting but there is a box on the right side of the Chagne Request that is "Next Action". On Next Action there is an option to prefill estimate. This:

Prefills cost estimate columns with amounts from price columns in the price/cost estimate grid. You can change any of the prefilled amounts as needed.

The Prefill Estimate button works only as a prefilling tool. If you change a price amount that previously prefilled in a cost estimate column, the cost estimate amount is not automatically revised; you must manually change it to match the price amount or you can click [Next Action] > Prefill Estimate again.

When you click [Next Action] > Prefill Estimate after you already prefilled estimates or manually entered them, you have the option to keep all the existing cost estimate amounts (cancel the prefilling) or clear and prefill them all with price amounts.

You cannot prefill a cost estimate if a change request's status is Approved and you do not have task security to edit approved change requests (if you use security)