Hey c25kd! Thanks for the suggestion. Adding mushroom farming to AutoFarm is an interesting idea. However, I want to make sure I understand your use case correctly.
By "small hitboxes", I would assume that you're farming small mushrooms in a cave, using the game mechanic where mushrooms spread to nearby blocks if it's dark enough. However, with this type of farm, AutoFarm would have no way of knowing which muchrooms it's meant to harvest and which ones it must keep to ensure that your farm won't stop working.
An easier way to farm mushrooms might be to turn them into giant mushrooms and then harvest the giant mushroom blocks with Nuker.