BuddyPress Notifications Code prepared for drop down menu. Added CSS for simple navigation output

functions.php

<?php

function bp_notification_badge() {
 
 	if ( is_user_logged_in() ) {
 
	 	echo '<ul class="noti_nav">';
 
	 	$notifications = bp_core_get_notifications_for_user( bp_loggedin_user_id() );
 
	        if ( $notifications ) {
	            $counter = 0;
	            for ( $i = 0; $i < count($notifications); $i++ ) {
	                $badge = count($notifications);
					echo '<li><a>'.$badge.'</a>';
					echo '<ul class="sub_noti_nav">';
	                echo '<li>'.$notifications[$i].'</li>';
					echo '</ul>';
	            }

	        }
		echo '</li>';
		echo '</ul>';
	}
 
}

?>

style.css

.noti_nav li {
    position: relative;
}
.sub_noti_nav {
    display: none;
    position: absolute;
    left: 0;
    top: 100%;
}
.noti_nav li:hover .sub_noti_nav {
    display: block;
}