You can undo multiple steps in your Photoshop document using Control + Z (Win) / Command + Z (Mac). This new multiple undo mode is enabled by default.
To perform undo or redo operation, do the following:
Undo: Moves one step back in the undo chain. Choose Edit > Undo or use the keyboard shortcut Control + Z (Win) / Command + Z (Mac).
Redo: Moves one step forward. Choose Edit > Redo or use the keyboard shortcut Shift + Control + Z (Win) / Shift + Command + Z (Mac).
The Edit menu also displays the name of the step that will be undone next to the Undo and Redo commands. For example, Edit > Undo Edit Type.
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