iPhone 15 Pro Gets New Silent Mode Bell Icon That Can Be Hidden

New silent bell icon shows in iPhone 15 Pro status bar when silent mode is on.
You can hide the silent bell icon by going to Settings > Sounds & Haptics and toggling off "Show in Status Bar".
The new Action button on iPhone 15 Pro controls silent mode by default.
Action button can be customized to control other features like camera, flashlight, etc.
Even if Action button is customized, silent mode can still be turned on/off from Control Center or Settings.

9to5mac.com

Relevant topic timeline:

9/13/2023

iPhone 15 Pro Gets New Customizable Action Button, Dynamic Island, and USB-C

Apple has announced that the new iPhone 15 Pro models will replace the traditional Ring-Silent switch with a new Action button, allowing users to customize its functionality and toggle between silent and ring modes.

10/3/2023

Customize iPhone 15 Pro's New Action Button with Multi-Purpose Shortcuts

The iPhone 15 Pro has replaced the mute switch with a multi-function Action Button that can be assigned to various tasks, including activating the flashlight and turning on the camera, and can be customized with shortcuts for more efficient use.