joplin/packages/app-cli/tests/support/plugins/simple/index.js

joplin.plugins.register({
	onStart: async function() {
		// const folder = await joplin.data.post(['folders'], null, { title: "my plugin folder" });
		// await joplin.data.post(['notes'], null, { parent_id: folder.id, title: "testing plugin!" });

		await joplin.commands.register({
			name: 'updateCurrentNote',
			label: 'Update current note via the data API',
			iconName: 'fas fa-music',
			execute: async () => {
				const noteIds = await joplin.workspace.selectedNoteIds();
				const noteId = noteIds.length === 1 ? noteIds[0] : null;
				if (!noteId) return;
				console.info('Modifying current note...');
				await joplin.data.put(['notes', noteId], null, { body: "New note body " + Date.now() });
			},
		});

		await joplin.views.toolbarButtons.create('updateCurrentNoteButton', 'updateCurrentNote', 'editorToolbar');		
	},
});