Hi Sunminjang,
Thanks for using Syncfusion product.
You can achieve your requirement by increment the row and column count of the current GridControl, when the horizontal or vertical ScrollBar reaches the end. We have prepared the sample based on your requirement please find the sample in the below attachment.
In that sample when we click the down or right RepeatButton in the ScrollBar, it will increment the row or column count of the inner GridControl as like in Excel.
Please let us know if you have any queries.
Regards,
Ponraja
SpreadsheetDemo_3659508f.zip