Collapse Nova 4.20+ Menu By Default

NovaServiceProvider.php

Nova::mainMenu(function (Request $request, Menu $menu) {
    $menu->items->each(function ($m) {
        if ($m instanceof MenuSection && $m->items->isNotEmpty()) {
            $m->collapsedByDefault();

            $m->items->each(function ($m) {
                if ($m instanceof MenuGroup && $m->items->isNotEmpty()) {
                    $m->collapsedByDefault();
                }
            });
        }
    });

    return $menu;
});