Hi, Sassie
Welcome to the forum!
I would try using them as green manure on the garden beds or mixing them with mulch.
Sassie said, "can the leaves be used for fermented plant juice, or plant teas or mulching around plantS like comfrey leaves.
If you are talking about a ferment or tea to pour over the garden that might make a great experiment, I doubt it would have the same effect as comfrey.
Comfrey (Symphytum species) is a great dynamic accumulator where tomato leaves may not be.
It sounds like you are having great success with potatoes.