The editor: duplicate, copy and paste; prefabs and sub-assets

Duplicate (Ctrl+D, Edit and Hierarchy menus) puts a copy beside the selection, named as Unity names it ("Cube (1)", then "(2)"), and selects it. Copy and Cut put the selection's subtree on the system clipboard as JSON ({"tassix_objects": [...]}, so it pastes into another editor window or reaches an agent); Paste adds it after the selection. Copies get fresh ids: references inside the copy follow it, references out keep pointing where they did. Each is one Restore batch, one undo step; other text on the clipboard pastes nothing.
The asset picker offers what's inside files: a model's meshes and a sheet's sprites, from the .meta's ID tables (internalIDToNameTable, the older fileIDToRecycleName, and nameFileIdTable nested in spriteSheet), as "Assets/Models/Car.fbx/Wheel". GameObject and Transform fields in a Unity scene can name a prefab: its root GameObject or Transform by the file ID in the prefab (the Transform without a parent), so saving writes {fileID: <root>, guid: <prefab>, type: 3} as Unity does. Reference lists scroll.
Tests: ids, references and names of copies; duplicate, copy, paste and undo with the platform's events (kittest); meta tables of both kinds and a nested sprite table; Coin Dash's prefab root; CameraFollow.target set to the Coin prefab in the inspector and saved into the .unity file.
Not yet: handles and grid drawn over objects; dragging prefabs into the scene (instancing a prefab in the editor's scene).