The action currently selected in OF will be listed in the border of any fully expanded app window (or at the top left of the desktop) if you:

1. Install the free Geektool pref pane,
2. Place GeekOFSQL.scpt (in the zip below) in your OmniFocus Scripts folder, so that its path is ~/Library/Scripts/Applications/Omnifocus/GeekOFSQL.scpt (where ~ is your home folder),
3. Dbl-Click the CurrentAction.glet XML file (also in the zip below), and click OK to install the geeklet.