Add beef broth to a 6-quart slow cooker. Add beef chunks in a single layer, and sprinkle salt and thyme over the beef. Drizzle balsamic vinegar on top.
Evenly distribute carrots and onions over the beef. Pour can of crushed tomatoes on top.
Cover and cook on high for 5 hours. Uncover and transfer the beef to a plate, leaving everything else including the liquid in the slow cooker. Use 2 forks to shred the beef.
Add rigatoni pasta to the slow cooker, stirring with the liquid. The rigatoni should be completely submerged. Evenly distribute the shredded beef on top of the rigatoni, patting it down to make contact with the liquid.
Cover and cook on high for 45 minutes. Uncover and taste the rigatoni for doneness. If not tender yet, stir and cook on high for another 30 minutes or until cooked through.
Stir and serve hot. Top with grated parmesan cheese and chopped parsley.