Gmail Shortcuts Plus от Gaurav Patidar

Gmail Shortcuts Plus makes it faster to move through open Gmail conversations using customizable keyboard shortcuts.

By default:

• Left Arrow moves to the previous email
• Right Arrow moves to the next email

You can change the keys from the popup, temporarily disable the feature, or reset everything back to the defaults.

Privacy: This extension runs only on Gmail pages and stores your settings locally in your browser. It does not collect, read, transmit, sell, or share your email content or personal data, and it does not send data to any external service.

Open source: The source code is available on GitHub.