You can create MileSplit Exports from Reports that have MileSplit Report Sections added to them. So, if you need to generate a MileSplit Export, first you need to create a Report that includes MileSplit Report Sections for each Event you have in your Race, then export that Report using the new MIleSplit Export Option.
It’s important to not change the order of the Report Sections that are generated for each Scored Event when you add them to the Report. They must be grouped together by Scored Event in order to meet MileSplit’s required formatting.