There are a few shortcut keys that can quite useful inside a branch hierarchy or tracking changes visualization.
In a branch hierarchy visualization, pressing the Insert while on a node with children (+ visible) drops down the child branch selector. Pressing Shift + Insert shows the general branch selection panel. Pressing Delete (x visible) removes the selected branch node. Pressing Home moves the selection to the branch node whose hierarchy is being viewed.
In the tracking changeset visualization, pressing Alt+L switches to the timeline view and pressing Alt+I switches to the hierarchy view. Pressing Home moves the selection to the starting branch (node or bar depending on the view) containing the changeset being tracked.
In both visualizations, the arrow keys move the branch selection. Pressing Control+C copies the visualization to the clipboard.