The Schildenstein Trail is a beautiful, but quite technical trail. As it is officially a hiking trail, please give hikers right of way and respect the trail rules. Hence this trail is unsanctioned.
To be able to enjoy this trail, you should be comfortable riding S3 difficulty level. There are some really difficult sections, that require some trial skills.
This trail has everything: technical sections made of solid rock, tight switchbacks, roots, some loose stuff, and flowy sections. My advice: inspect a difficult sections before riding it and be prepared to get off your bike several times.