Forum:Help with Navbox with collapsible groups

Hello and thanks for the help in advance!

Basically what I am trying to do is make a navbox within a navbox for an OC Club on the Percy Jackson Fan Fiction Wiki, however I am not exactly sure how to do this. I copied over the Wikipedia Navbox with collapsible groups in hopes that that would work, but I don't believe it does (however has no idea). The wiki one can be viewed here.

Now I am trying to make one (Template:THO for the OC Club THO. Just a skeleton of it would be good, and then I can add the required information.  I really need help with this and would want to know how to do it.  Thanks!