Line the slow cooker with aluminum foil and set aside.
In a medium bowl, combine beef, sausage, onion, garlic, egg, panko, tomato paste, Italian seasoning, Worcestershire sauce, salt, and pepper until just blended. Do not overmix.
Place meat mixture in slow cooker and shape into an oval loaf.
In a small bowl, whisk together ketchup, brown sugar, balsamic vinegar, and Dijon mustard.
Spoon half the glaze over the meatloaf.
Cook on high for 3–4 hours or low for 6–7 hours, until meatloaf reaches 160 °F inside.
Using foil, lift meatloaf onto baking sheet. Broil on high for 3–4 minutes until glaze caramelizes.
Remove and rest for 10 minutes.
Slice and serve with remaining glaze.
Notes
Nutrition information is approximate and automatically calculated.