Halion like Cubase uses a database file to store ratings, tags etc. for the media bay. For Cubase this file can be manually backed up and copied back in after a clean install to restore your ratings.
Sonic and Halion each have their own .db files rather than a shared one.
You could make a backup of your Halion mediabay3.db file and copy Sonic’s one over to the containing Halion directory.
2 catches though. I don’t know if they are compatible and this will wipe all ratings you did in Halion. You can use your backup file to restore this of course.
I’m using a PC so the folder for the Halion mediabay3.db file is in …AppData\Roaming\Steinberg\HALion 5_64. Sonic’s .db file has the exact same name and should be in …AppData\Roaming\Steinberg\HALion Sonic_64.
Just make sure you have backups. I don’t want to be the cause of you losing all those Sonic or Halion ratings.