Overview
TreeClimbing makes all logs, when part of a tree, act like ladders, and leaves - again, when part of a tree - nonsolid when collided from below.The combination of these two things means you can now climb up trees' trunks, through their leaves, and stand on the canopy. This is enormously useful when paired with something like the OpenBlocks hang glider.
You can also sneak while on leaves to fall through.
There is significant effort put into mod compatibility - it works off the same DragonAPI registry as the RC woodcutter and bedrock axe - so it should work for most modded tree types. Trees which use existing log/leaf blocks, but in novel pairings, are likely to not be recognized.