Selecting
Selecting in the viewport
Double-click a surface to select the node that draws it. Solidly outlines the selection in the viewport, reveals the matching row in the sidebar hierarchy, and switches the inspector to its Node tab.
Clear the selection by pressing Esc or by single-clicking empty space.
The selection outline's colour and width are set in Settings ▸ Viewport ▸ Selection.
Selecting in the hierarchy
The sidebar's Hierarchy mode selects the same thing the viewport does, and the two stay in step. Select several rows with ⇧-click for a range and ⌘-click for individual rows, which enables the multi-node operations described in Editing the hierarchy.
Instanced copies
A node drawn many times, through a glTF EXT_mesh_gpu_instancing attribute, a USD PointInstancer, or a native USD instance, appears in the hierarchy with a row per copy underneath it. Selecting one of those rows selects that single copy rather than the node that draws the batch, and the transform gizmo moves to that copy's own position.
The distinction matters for deletion. With a copy selected, ⌘⌫ is labelled Delete Instance and removes that one placement. With the node itself selected.
Transforming a selection
Selecting a mesh node in a format Solidly can edit draws a transform gizmo at the node's pivot. See Transforms.
Selecting in Photo Mode
Photo Mode replaces double-click node picking with focus picking: double-clicking a surface sets the depth-of-field focus distance to that point. See Photo Mode.