In SB you can make a separate document "tree.ccb" and give it a custom class Tree. The Tree class could then, in its didLoadFromCCB method, vary the default editor positions of leaves and branches, vary their sprite frames and other properties.
Alternatively you could design multiple variants of the tree in SB by putting each variant in its own node group, then at runtime randomly pick one of the Tree node's children (containing the nodes that define one of the trees) and remove the others. That way you can design all variants in SB and still have random trees in the game.
In SB you'll have to use the eye symbol to show only the tree you're currently editing, to make things easier. At the same time if you enable all trees in SB, you could quickly see if any of the trees exceed a given size (if needed).