Set a Focus mode on macOS Monterey (12.0+) using JavaScript for Automation (JXA)

set-focus-mode.js

function toggleFocus(focus) {

	const app = Application("System Preferences")
	const pane = app.panes.byId("com.apple.preference.notifications").anchors.byName("Focus")
	app.reveal(pane) // Open the preference pane

	// Useful way of inspecting the UI hierarchy of an open app:
	// Application("System Events").applicationProcesses.byName("System Preferences").entireContents()
	const ui = Application("System Events").applicationProcesses.byName("System Preferences").windows.byName("Notifications & Focus").tabGroups.at(0)

	delay(0.5) // Ensure the UI has loaded

	const rows = ui.scrollAreas.at(0).tables.at(0).rows()
	rows.forEach(row => {
		let name = row.uiElements.at(0).staticTexts.name()
		if (name == focus) {
			row.select() // Select the focus mode, if found...
			ui.groups.at(0).checkboxes.at(0).click() // ... and toggle the switch
		}
	})
	app.quit()
}

toggleFocus("Do Not Disturb") // Or whichever you like