Which panel must be open to create an action in Photoshop?

To create an action in Photoshop, the Actions panel must be open. This panel allows users to record a sequence of commands and operations performed within Photoshop, which can then be saved and reused later. Actions streamline workflows by automating repetitive tasks, enabling users to apply the same series of edits or effects across multiple images with a single click.

The Actions panel provides essential features such as the ability to start and stop recording actions, organize recorded steps, and preview or play back those actions as needed. Without this specific panel, users would not have access to the tools necessary for creating and managing actions, rendering the process impossible.

While the Layers panel, History panel, and Color panel may all serve important roles in various editing processes, they do not facilitate the creation or management of actions. Rather, they focus on aspects like layer manipulation, tracking changes, and adjusting color settings, respectively. Therefore, having the Actions panel open is critical when setting up and using actions in Photoshop.