The MuseScore plugin (extension) world is, ugh, not great.

They are currently reworking the plugin ecosytem, moving towards extension over plugins.

There is no documentation for plugins or extensions.

Best you can do is copy existing and guess what the code means.

My best idea currently is to download other existing plugins (if the right version, and if they work). I’ll save my own development for after the team gets it together.

Extensions

Extensions use a manifest.json file and .js files. I like this idea, but currently lacking any documentation.

Plugins

Plugins are still a thing for MuseScore 4, although being phased out?