Filament Create/Edit Pages: Add Cluster-like Sub-Navigation Items

Filament allows you to build Clusters (a grouped second-level navigation). But typically, it's only for List pages. What if we want to have them in the Create/Edit pages:

To do this, there's a straightforward function we can add:

app/Filament/Resources/UserResource/Pages/CreateUser.php

class CreateUser extends CreateRecord
{
    protected static string $resource = UserResource::class;
 
    public function getSubNavigation(): array
    {
        if (filled($cluster = static::getCluster())) {
            return $this->generateNavigationItems($cluster::getClusteredComponents());
        }
 
        return [];
    }
}

This will render our Cluster as Sub Navigation.

The same works for the Edit page:

app/Filament/Resources/UserResource/Pages/EditUser.php

class EditUser extends EditRecord
{
    protected static string $resource = UserResource::class;
 
    protected function getHeaderActions(): array
    {
        return [
            Actions\DeleteAction::make(),
        ];
    }
 
    public function getSubNavigation(): array
    {
        if (filled($cluster = static::getCluster())) {
            return $this->generateNavigationItems($cluster::getClusteredComponents());
        }
 
        return [];
    }
}