Manfred has whipped up a LaunchBar action for browsing your Keyboard Maestro macros:
The action lists all macros available in the current context. Convenient access to the macros is possible just by browsing the Keyboard Maestro application (using the right arrow or space key). Return triggers the selected macro. Needless to say: The list of macros supports LaunchBar’s abbreviation search (to narrow down the list) and Instant Open (to open the macro of choice even quicker) as well.
Works as described and is pretty damned sweet.