Example of how to break down the payments within a transaction and display each individual payment in the CSV.

csv_payments.php

<?php //Please do not include the opening PHP tag if you already have one

function tw_ee_espresso_reg_report_filter_columns_reg_paid( $csv_row, $registration_db_row ) {
	$registration = EEM_Registration::instance()->get_one_by_ID($registration_db_row['Registration.REG_ID']);
	$reg_payments = $registration->registration_payments();
	
	if(!empty($reg_payments) ) {
		
		//Set up our variables for use below.
		$amount_paid = 0;
		$individual_payments = array();
    
		foreach($reg_payments as $reg_payment) {
			//Loops through each payment on the registration and build out our variables.
			$payment = $reg_payment->payment();
			$amount_paid += $payment->amount();
			$individual_payments[]= $payment->amount();
		}
		
		//Use the variables above to replace the current values in the CSV.
		$csv_row['Amount Paid'] = $amount_paid . ' (' . implode(',', $individual_payments) . ')';	
	}
	
	return $csv_row;
}
add_filter( 'FHEE__EventEspressoBatchRequest__JobHandlers__RegistrationsReport__reg_csv_array', 'tw_ee_espresso_reg_report_filter_columns_reg_paid', 20, 2);