XMonad.Actions.TreeSelect
TreeSelect displays your workspaces or actions in a Tree-like format. You can select the desired workspace/action with the cursor or hjkl keys.
This module is fully configurable and very useful if you like to have a lot of workspaces.
Only the nodes up to the currently selected are displayed. This will be configurable in the near future by changing ts_hidechildren to False, this is not yet implemented.