Hi,
Something I would suggest: in Navisworks 2012, we provided a plugin of .NET called Dockable window, in which you could use Tree control of .NET. When any node of the tree is selected, you can create a Search condition (.NET API) to find the corresponding objects, and highlight them. For sure you could also add node like Compact, SelectionSet etc. It just depends on the search condition.
At COM side, \api\COM\examples\PLUGIN_07 is a sample to build one tab within the built-in Selection Tree pane. In this tab, you can specify the conditions (Find API of COM) thus the corresponding nodes will be listed, either explicit selection, search selection etc. But I prefer to the .NET plugin because it would be more flexible.
Regards,
Xiaodong Liang
Developer Technical Services