Classify
Classify places the parts of an assembly library on a trait chart, as its own step on the assembly wire. It is the same chart that the Assembly Decoration and Clusters Decoration have inside, and most of the time you'll classify parts there, on the decoration's own traits. Traits explains how parts are matched to the tree. Place Classify from the toolbar's Assemblies menu, after an Assembly Resource.
The chart
First Dimension and Second Dimension name the two traits on the chart's axes (condition and exposure by default), each with a Range. Nothing in Natsura writes condition or exposure on a tree: they are names to match against attributes you provide, so set the axes to attributes the tree carries, such as height or elevation_angle, or to ones you write in a Wrangle. Press Enter (or Classify (Enter)) to open the chart, and drag parts from the row below it onto the chart. Shift-drag adds parts to the selection and Ctrl-drag removes them, a middle-mouse drag lines the selected parts up, and N toggles Normalize Scale, which shows the parts at a similar size on the chart. Reset Classifications sends every part back off the chart.
Remove Unclassified, under Advanced, drops the parts you left off the chart. Group and Pieces, under Input, pick which parts are classified and which attribute names them.
Output
The output is the library with each part's trait values written onto it. Wire it into an Assembly Decoration's first input, or into another Classify. A decoration's chart starts each part at the value it already has for an axis trait, and dragging the part there overrides it.
Status
A Classify placed on its own can show an error from its default override settings, which expect a decoration around it. A decoration's trait picker doesn't offer the traits a Classify wrote.
Build Assembly Rig
Build Assembly Rig is the automatic rigging step inside the Assembly Resource. It works out which part attaches to which from their pivots and builds the rig that lets parts bend and stay instances.
Clusters Decoration
Clusters Decoration bends parts from a library along the branches they sit on, sharing each bent shape between similar branches so the copies stay instances.