I couldn't find a path to do it from the Step-by-Step View. So I switched to Form View, navigated to form 1040-X, then entered the amount I wanted to be applied to my 2025 ES tax in line 23, and TurboTax automatically calculated the amount to be refunded to me in line 22.
The reason for not asking for the full refund, is that it usually takes several weeks. In the past several years ago, when I had a refund after an amendment, I had asked for the full refund, thinking that I would get it before the next ES taxes were due. However, due to the delay, I ended up having to disburse the ES payment before the refund.
I hope this helps.