Writing a mousepad plugin is actually a bit of a pain.

Note that you'll need all the Mousepad code to build your plugin, as the headers are not installed. We've never gone so far as to actually expose an API for writing plugins, choosing which headers should be installed and documenting this properly.

Which mostly means that you're on your own.

Whilst building one for Ethersync _should_ be fairly easy (exec and ionotify should get 90% there), without documentation - how do you ensure the text buffer gets updated correctly...? I'm not surprised no one has put this together yet.