You can soften onions and celery with butter and garlic in a pan on your stovetop to cook them down a bit and become more fragrant, or just throw all of that into the slow cooker as is.
If you cook them down, empty into Crock when softened. Season with salt, pepper and dill. (can add 1 cup canned corn that is drained if you like now)
Stir in milk and broth. Then layer the egg noodles on top with the tuna on top of that. Do not stir together.
Close lid and set to high heat for 2 hours.
15 minutes before cook time ends, lift lid and stir all contents together. Top with cheese and top with the lid again so that can melt.