We have a Grid (actually a TreeGrid) with a number of column

The setColumnHidden is time consuming operation , becuase it require updating all rows in grid, but the using few such commands one by one even more time consuming, because each time it is separate update.

As far as I can see there is no any fast way to do such operation. Initially grid was designed to work with vertical sets ( few columns, many rows ) and setColumnHidden functionality was added as rare used extension, it was not purposed for such usage.

Please send an example of your xml file, which you are use in described situation, to dhtmlx@scand.com, I will check how code can be optimized, but in any case it will not be much faster.