Hey Martin,
You can't do much to reduce the Keyboard Maestro Editor's footprint.
You might consider making a formal feature request to be able to hide the group and macro panels though. That ought not to be too hard, so Peter might consider it.
I would probably use KMFAM for this:
But Mike has an interesting new offering that might be of use:
If I was going to palletize actions / groups-of-actions I'd bind the palette buttons to AppleScripts that would insert actions via XML contained IN the AppleScript – OR – I'd use a macro group of macros with template actions and script their insertion into the macro being edited.
-Chris