I understand that the current out-of-the-box feature only allow file to be downloaded in the format of xlsx. is there any option/setting where I can customize or change it to download as csv format?
You can simulate the chart/table in a script table and use the store command to write the table as a txt file with the format and extension of a csv file, but this can work with fixed filtered data (in example if you always want to export the current year or month data).