The leftAddon and rightAddon props are used to display another element inside the navigation item.
<>
<NavigationItem leftAddon={<Badge>12</Badge>} text="Navigation item" />
<NavigationItem rightAddon={<Badge>12</Badge>} text="Navigation item" />
</>
The isActive prop is used to display the navigation item as active.
<>
<NavigationItem isActive text="Main navigation item" />
</>