Should you want to get more creative with the Action Button, the Settings app is where to go. Open the app and scroll down until you find the Action Button tab.
The first thing you will notice is how different the user interface looks compared to other settings on the iPhone. There’s a fancy animation of the Action Button as you swipe through the programmable functions.
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Your options include Silent Mode (default), Focus, Camera, Flashlight, Voice Memo, Accessibility, Shortcut, and Translate (arriving later this year).
Apple allows you to map a specific function with the broader categories. For example, a drop-down box on the Camera slide gives you the options of Photo, Selfie, Video, Portrait, and Portrait Selfie.

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https://www.zdnet.com/article/how-to-use-the-iphone-15-pros-new-action-button-to-do-just-about-anything/