Gadget:displaytitle.js

const $h1 = $( '.mw-page-title-main' );
const title = $h1.text();
const origTitle = $( '.origTitle' ).text();
$h1.css( 'cursor', 'pointer' );
$h1.attr( 'data-title-change', '' );
$h1.on( 'click', () => {
	if ( $h1.attr( 'data-title-change' ) === undefined ) {
		$h1.text( title );
		$h1.attr( 'data-title-change', '' );
	} else {
		$h1.text( origTitle );
		$h1.removeAttr( 'data-title-change' );
	}
} );