If you are running Stylus RMX on a Mac, please login into the Spectrasonics website and download the latest update for Stylus RMX. The update includes a built-in function to import REX files.
Please view the links below for further instructions and information.
Install latest update
https://www.spectrasonics.net/support/knowledgebase_view_topic.php?id=120&categoryID=9
Importing REX Files
https://support.spectrasonics.net/manual/StylusRMX/1.9/en/topic/importing-rex-files-2
Guidlines
https://support.spectrasonics.net/manual/StylusRMX/1.9/en/topic/guidelines
Organising User Libraries
https://support.spectrasonics.net/manual/StylusRMX/1.9/en/topic/organizing-user-libraries