Hi Wladimir,
Thanks for using Syncfusion product.
By default, ExcelFilter has load all the record from binding object so if you load more than 100000 record unique values, obviously it will take a time to load that values in excel filter popup. In our GridGroupingControl architecture, does not have the limitation to load the records in filter popup when click on the excel filter icon.
Please let me know if you have any concerns.
Regards,
Mohanraj G