ShowButton
Specifies whether drop-down button will be shown inside column header.property ShowButton: Boolean read FShowButton write SetShowButton default False;
Remarks:
By default, clicking on this button open filtering options popup, but developer can override OnHeaderButtonClick event of column to open custom popup.
Example:
procedure TForm1.NxTextColumn61HeaderButtonClick(Sender: TObject; X, Y: Integer;
var Accept: Boolean);
begin
Accept := False; // Don't show default popup
PopupMenu1.Popup(X, Y); // Custom popup
end;