is it possible to have an item menu that is a TUniFileUploadButton ?
Can you try this?
procedure TMainForm.UniDBGrid1ColumnActionClick(Column: TUniDBGridColumn;
ButtonId: Integer);
begin
case ButtonId of
...
3 :
begin
UniFileUploadButton1.JSInterface.JSCall('fileInputEl.dom.click', []);
end;
end;
end;