Extract Data from Release Payments tab by pressing "Process and "Processing All"

You would have to intercept the processing delegate, normally you would do that via the Initialize method in a graph extension but it looks like this processing screen sets the delegate on the Row Selected event so you would want to override that. Code sample below.

    public class ReleasePaymentsExt : PXGraphExtension<APReleaseChecks>
    {
        public static bool IsActive() => true;
        public void ReleaseChecksFilter_RowSelected(PXCache sender, PXRowSelectedEventArgs e, PXRowSelected baseMethod)
        {
            baseMethod(sender, e);

            var baseDelegate = (PXProcessingBase<APPayment>.ProcessListDelegate)Base.APPaymentList.GetProcessDelegate();

            Base.APPaymentList.SetProcessDelegate((List<APPayment> payments) =>
            {
                baseDelegate(payments);
                //Your Code Here
            });

        }
    }