I created a custom AssetImportData class which inherits from AssetImportData. When I import the mesh it correctly has my custom AssetImportData along with the inherited SourceData. And the SourceData.RelativeFilename is correct. But when I close the editor and reopen the SourceData.RelativeFilename is empty, but my custom data is still there. Not sure if I’m not saving something correctly or what’s going on.