It depends on what you want to customize. Note that summary reports are exported from the HTML of the page (not from database data directly), so in general you may customize the export class and override the loadHtml() method to manipulate the HTML. Also read Customizing Export (v2021).
Thanks. I understand that I need to override ExportExcel::loadHtml() for a Summary Report.
However, the example using Config("EXPORT_CLASSES.excel", "MyExportExcel") says it is for tables only and not applicable to reports.
In PHPMaker 2025, how should I register or replace the ExportExcel class specifically for a Summary Report so that my overridden loadHtml() method is used?