Create Proxy
Create Proxy makes a simple stand-in shape for each piece of its input. Pieces are told apart by a name attribute, set in the name field under Input (name by default). It is a building block inside the assembly tools, including Build Assembly Rig, Import Assembly and Pivot Edit, and it is hidden from the Tab menu.
Settings
Proxy Type, under Process, picks the shape: Bounds, Oriented Bounds, Hull, Decomposition, Spheres, vdb, medial axis or particles. The Cluster, voxel, medial axis and PArticles folders below it hold the settings for the types that need them. Pre-process has Small Part Threshold (relative) and Remove Leaves, and Output Packed (on by default) packs the result.
Status
Create Proxy is an internal node. Its settings have no tooltips yet.
Core Decoration
Core Decoration is the base that every decoration is built on. It is hidden from the Tab menu, and you meet it only when building a decoration of your own.
Debug Tree Rig
Debug Tree Rig draws a tree's mesh, joints, skeleton and skin bindings so you can see a bad rig before export. It is the Debug view of Simplify Tree Rig and Skin, and hidden from the Tab menu.