The credit sublist values are not directly accessible using a script. However, we can create a workbook to fetch the credit data, and then use SQL to retrieve it in the script.
Steps:
Create a dataset for the required data. Navigate to Analytics > create new dataset.
We can filter the results by adding criteria.

After creating the dataset Click on the create workbook option:

Click on add all feilds to workbook option:

The columns will be added to the workbook now:

Click on save & save the workbook.
Use the export as script option to get the SQL after saving the workbook:

The SQL can be copied and can be used in script (similar to exporting saved serach).

Script part:
Here the internal id of the payment should be passed to the function as transactionId:
/**
* Function to get credit data using SQL query
* @param {string} transactionId
* @returns {Array}
*/
function getCreditData(transactionId) {
try{
let sql = "SELECT BUILTIN_RESULT.TYPE_DATE(AppliedCreditTransactionLineLink_SUB.trandate) AS trandate, BUILTIN_RESULT.TYPE_STRING(BUILTIN.DF(AppliedCreditTransactionLineLink_SUB.nexttype)) AS nexttype, BUILTIN_RESULT.TYPE_STRING(BUILTIN.DF(AppliedCreditTransactionLineLink_SUB.nextdoc)) AS nextdoc, BUILTIN_RESULT.TYPE_STRING(BUILTIN.DF(AppliedCreditTransactionLineLink_SUB.previousdoc)) AS previousdoc, BUILTIN_RESULT.TYPE_CURRENCY(BUILTIN.CONSOLIDATE(AppliedCreditTransactionLineLink_SUB.foreignamount, 'INCOME', 'NONE', 'DEFAULT', 0, 0, 'DEFAULT'), BUILTIN.CURRENCY(BUILTIN.CONSOLIDATE(AppliedCreditTransactionLineLink_SUB.foreignamount, 'INCOME', 'NONE', 'DEFAULT', 0, 0, 'DEFAULT'))) AS foreignamount FROM TRANSACTION, (SELECT AppliedCreditTransactionLineLink.paymenttransaction AS paymenttransaction, AppliedCreditTransactionLineLink.paymenttransaction AS paymenttransaction_join, transaction_0.trandate AS trandate, AppliedCreditTransactionLineLink.nexttype AS nexttype, AppliedCreditTransactionLineLink.nextdoc AS nextdoc, AppliedCreditTransactionLineLink.previousdoc AS previousdoc, AppliedCreditTransactionLineLink.foreignamount AS foreignamount FROM AppliedCreditTransactionLineLink, TRANSACTION transaction_0 WHERE AppliedCreditTransactionLineLink.nextdoc = transaction_0.ID(+) ) AppliedCreditTransactionLineLink_SUB WHERE TRANSACTION.ID = AppliedCreditTransactionLineLink_SUB.paymenttransaction(+) AND TRANSACTION.ID = ? ";
let results = query.runSuiteQL({
query: sql,
params: [transactionId]
});
return results.asMappedResults();
}catch(e){
log.error("error@getCreditData",e);
}
}