Create a new snapshot

Alt + New Snapshot

Option + New Snapshot

Rename snapshot

Double-click snapshot name

Double-click snapshot name

Step forward through image states

Control + Shift + Z

Command + Shift + Z

Step backward through image states

Control + Alt + Z

Command + Option + Z

Duplicate any image state, except the current state

Alt-click the image state

Option-click the image state

Permanently clear history (no Undo)

Alt + Clear History (in History palette pop‑up menu)

Option + Clear History (in History palette pop‑up menu)