Even though they aren't readily displayed, the items that were present in CRM 2011's left navigation to related entities still exist. The SDK provides supported functionality to hide and show these links but the problem is that you need to find the Id of the specific navigation item in order to do so. Knowing this Id would also come in handy if you are going to the CRM 2013 Quick Navigation solution I've created and you want to limit which related entities are shown.
Unfortunately the Id we need in both cases isn't exposed through CRM's UI anyplace so we need to actually look at the HTML content of the page to figure this out.
Start out by opening a record and hovering over the record on the navigation bar to drop down the related entities.
Using Internet Explorer or Google Chrome hit the F12 key to bring up the developer tools.
Use the "Inspect Element" button and then select the specific item from the navigation. You should then see the HTML content below change, from here we can grab the Id on the navigation item.
If we look to the <a> tag and check the id attribute we should see something like "Node_navContacts". We are after the last part, "navContacts". This is the Id we need to use to identify the specific navigation item.
Internet Explorer 11 (Looks different than previous versions)