FYI for other users of this plugin:
I encountered an issue where this plugin prevented a correct shutdown and restart of Musicbee 3.5:https://getmusicbee.com/forum/index.php?topic=36499.0
I have not tested whether the plugin functionality still works on MusicBee 3.5, but I doubt it given this experience.
The plugin did still work with MusicBee 3.4.
Perhaps it's related to the upgrade to .NET 4.8 of MusicBee 3.5.