Zipper Tree ?

gistfile1.hs

tree :: Tree Int
tree = Node 1 [ Node 2 [], Node 3 [] ]
       
test = zipper tree
	& downward branches
	& withins traverse
	<&> downward root 
	<&> focus %~ (\x -> x + 10)
	<&> rezip
-- Node {rootLabel = 1, subForest = [Node {rootLabel = 12, subForest = []},Node {rootLabel = 3, subForest = []}]}