You are free to display any Flex component in a view that you "own", i.e. a central view, whether it is an Object summary view portlet, a view in a sub-tab of Manage or Monitor, or a global view.
But you cannot change the views that you don't own (i.e. there are no public extension points for those), in particular:
- The Left-hand side and right-hand side areas
- Any existing vSphere object views
So your tree will have to be displayed in your own custom view.