use Outl1ne\MultiselectField\Multiselect;

public function fields(Request $request)
{
    return [
      Multiselect::make('Football teams')
        ->options([
          'liverpool' => 'Liverpool FC',
          'tottenham' => 'Tottenham Hotspur',
        ])

        // Optional:
        ->placeholder('Choose football teams') // Placeholder text
        ->max(4) // Maximum number of items the user can choose
        ->saveAsJSON() // Saves value as JSON if the database column is of JSON type
        ->optionsLimit(5) // How many items to display at once
        ->reorderable() // Allows reordering functionality
        ->singleSelect() // If you want a searchable single select field
        ->distinct('football') // Disables values used by other multiselects in same distinct group
        ->taggable() // Possible to add values ("tags") on the fly

        // Async model querying
        Multiselect::make('Artists')
          ->asyncResource(Artist::class),

          // If you want a custom search, create your own endpoint:
          ->api('/api/multiselect/artists?something=false', Artist::class),
    ];
}

->options([
    'MS' => ['label' => 'Small', 'group' => 'Men Sizes'],
    'MM' => ['label' => 'Medium', 'group' => 'Men Sizes'],
    'WS' => ['label' => 'Small', 'group' => 'Women Sizes'],
    'WM' => ['label' => 'Medium', 'group' => 'Women Sizes'],
])

Multiselect::make('Country', 'country')
    ->options([
        'IT' => 'Italy',
        'SG' => 'Singapore',
    ]),

Multiselect::make('Language', 'language')
    ->optionsDependOn('country', [
        'IT' => [
            'it' => 'Italian',
        ],
        'SG' => [
            'en' => 'English',
            'ms' => 'Malay',
            'zh' => 'Chinese',
        ]
    ]),

    // Optionally define max number of values
    ->optionsDependOnMax([
        'IT' => 1,
        'SG' => 3,
    ])

// Add your BelongsToMany relationship to your model:
public function categories()
{
    return $this->belongsToMany(\App\Models\Category::class);
}

// Add the field to your Resource for asynchronous option querying:
Multiselect::make('Categories', 'categories')
  ->belongsToMany(\App\Nova\Resources\Category::class),

// Alternatively, you can set the second argument to 'false' to
// query the options on page load and prevent the user from having
// to first type in order to view the available options. Note: Not
// recommended for unbounded relationship row counts.
Multiselect::make('Categories', 'categories')
  ->belongsToMany(\App\Nova\Resources\Category::class, false),