monline

There're several approaches that work pretty well.

1. The official method is to use the ignore_file directive in munin-node.conf. It already contains a couple of regexp patterns that exclude various plugin filenames. Eg. renaming your plugin file to "*.bak" disables it.
2. You can add a command /bin/true directive for the respective plugin to the plugin-conf.d/munin-node file.

PS: this comes handy in case you used to store your custom plugins right in /etc/munin/plugins. Of course you could set up a directory eg. in /usr/local/munin/plugins and use symlinks ... and disabling a custom plugin could be solved as usually, by removing the symlink from /etc/munin/plugins. It's up to you.

PS2: if you rename a plugin file in /etc/munin/plugins to "*.bak" and create a symlink on this disabled plugin, then the symlink will be disabled as well. Or at least that's what I experienced.