The help (console and CHM) for PLUGIN suggests that you can see the commands and functions (but not variables?) in a single plugin:
But it doesn't work. In fact, I don't really understand that line (above) from the help. It seems to be saying you can follow (or precede?) any option but "/V" with w plugin name.
Usage : PLUGIN [/B plugin /C /F /I plugin /K /L plugin /P /U plugin /V]