This is not in the javascriptaction Export_To_Excel and the used library is not editable. You can either wait until it is implemented or create a custom Excel export with the Excel module for the Marketpleace. The configuration attribute of DG holds a JSON representation of the columns. With a JSON import template you can put that in a non-persistable structure. With that structure change the the template and remove the hidden columns on the fly (don't commit them or make a copy of the template on before). This is quite a lot of work.