Is there a purpose to having the stacked admin navigation on the admin>plugins page? Looking at the code in plugins.hbs
it seems that all it can do is display one item, and that item is for the page the the user is currently on.
<div class="admin-nav pull-left">
<ul class="nav nav-stacked">
{{nav-item route='adminPlugins.index' label="admin.plugins.title"}}
{{#each route in adminRoutes}}
{{nav-item route=route.full_location label=route.label}}
{{/each}}
</ul>
</div>