Currently the TAdvGridExcelIO component only supports up until Excel 2003. This means you cannot export something with more than 256 columns. Exporting to Excel 2007 format with more than 256 columns would be great.

TAdvGridExcelIO: Support excel 2007

Topic		Replies	Views
TAdvGridExcelIO has a Max_Columns of 255 which is less than the current limit for Excel VCL Feature Requests	1	187	January 19, 2023
TAdvGridExcelIO with Native XLSX VCL Feature Requests vcl-ui-pack	3	88	January 13, 2022
Grid column filtering - emulating Excel 2007+ VCL Feature Requests vcl-ui-pack	0	86	November 7, 2013
Displaying Excel files TMS VCL UI Pack	1	162	December 12, 2023
TMSAdvGrid and XLS export, max exportable rows TMS VCL UI Pack	1	275	August 9, 2021