The new Heap Walker is great and everything, but there is a serious usability
problem: there are no navigation controls.

Walking through a heap frequently involves navigating through multiple levels of
references between objects.  For example, if when examining an instance of a
class I right-click on "this" and choose Find Nearest GC Root the Heap Walker
will expand the tree in the references window.

If I right-click one of the references in the expanded tree and choose Show
Instance the Heap Walker will change the display so that I am seeing that object
instance.  But now, how do I get back to the object instance that I was looking
at?  

This is pretty painful... seems like back and forward arrows would really help here.