There is an 'Export to Excel' JS action you can call from a nanoflow. You need to pass the name of the DG2 widget and a few other parameters for that.
I also had the issue that i updated the widget and the new export didnt show. Here is how i solved it:
Go to the Marketplace Modules in your Studio Pro (left side)
I believe (others please correct me if I'm wrong) DataGridd2 don't yet support export to excel, you should create custom logic for that here is a link to post.