Select Object

Select Object (O) selects an object from the render exactly, by reading the Cryptomatte Object pass.

1. In Layers ▸ Ground & Depth, click Enable Passes (it turns on Depth and Cryptomatte Object), then render.
2. Press O and click an object. Shift and Alt add and subtract.
3. Shift+Enter saves it as a live CS Objects selection: a Cryptomatte node that follows the object on every frame.