joplin/packages/app-desktop/services/plugins/plugin_index.html

<html>
<head>
	<script src="./plugin_index.js"></script>
	<script>
		// joplin.plugins.register({
		// 	onStart: async function() {
		// 		alert('PLUGIN STARTED');
		// 	},
		// });
	</script>
</head>

</html>