in direction Feldkirch they are already mapped: https://www.openstreetmap.org/relation/13544807#map=15/47.4786/9.7004&layers=O but there are some missing parts in the relations. Also the other direction is missing. VVV calls the trains "S5", ÖBB just "R" (because they don't stop in every station like a S-Bahn). In the next timetable period, starting with 11th December, ÖBB will call these trains as line "R5".