If you are developing a feature to "Download [Report] as XLSX," it generally follows these steps:
If you can tell me the you are using (e.g., SAP, Salesforce, or a custom app), I can give you more specific instructions on how to locate or trigger that download.
Use a library to generate the XLSX file. Unlike older binary formats, XLSX is an Open XML standard that is widely compatible with modern spreadsheet tools like Google Sheets or LibreOffice.
It may represent a specific system command or API endpoint used to trigger a data export.