+ completely unused in current keymaps, never fully implemented
- overlays
+ almost completely unused in current keymaps
+ - key behaviors
+ + used to implement radio groups and overlays, and to deal with things
+ like keys that physically lock; unused in current keymaps
- indicator behaviours such as LED-controls-key
+ the only supported LED behaviour is key-controls-LED; again this
was never really used in current keymaps