Any other navigation tab can show the number of unread posts by configuring it to use a callback for the badge with class name "AL\UnreadPostCount\Callback" and method "getUnreadPostCount". This is the default setup for "What's New" button after add-on installation.
The badge is added using default XenForo 2.x layout/styling, but it can be easily styled for each case using CSS only by using "nav{navigationItemIdHere}" class. For example:
CSS:
.customBadgeContainer.navwhatsNew:after {
top: -10px;
}
will make the badge in What's New tab to be on the top-right corner.
The product is free and does not include any licensing code or any callbacks.
Feel free to suggest further enhancements for the add-on or report any issues you have and they will be addressed asap.
Please consider posting a review if you are using the add-on and let us and other users know how it works for you.
Thank you!