When you right click in the feature tree, there is a "Collapse Items" command.  When you assign a shortcut key to this, you can see the name of the command as "Expand/Collapse Tree"

I use this shortcut all the time to "Collapse" the tree.  However, for the life of me, I can't figure out how to "Expand" the tree.  I need it to expand all sub-assemblies in a top level assembly (there could be 100s).

Does anybody know how to make this work?