Do you have a sample of the import file format that Tradestation accepts? Chances are you can design a custom file format with Tickstory that will work. If it is successful, we can look at adding it as a pre-defined format.
At this stage, the best way to potentially do this at the moment is export the data to a comma-delimited file or Excel spreadsheet and perform a macro to convert it. We've added a note about how we can support a JSON export in the future.