Add + button next to select button in repeater conditionally

        return [
            Select::make('product_id')
                (.....)
                //====>>>> This is the part of the code the question is about <<<<<============
                ->when(!filled('product'), function (Select $select) {
                    return $select
                        ->relationship('product', 'description', function (Builder $query, Get $get) {
                            $query->where('brand_id', '=', $get('../../brand_id'));
                        })
                        ->getOptionLabelFromRecordUsing(fn(Product $product): ?string => $product->description)
                        ->createOptionForm(function (Get $get) {
                            return [
                                Hidden::make('brand_id')
                                    ->default($get('../../brand_id')),
                                Hidden::make('supplier_id')
                                    ->default($get('../../supplier_id')),
                                TextInput::make('item_code')
                                    ->label('Artikelcode')
                                    ->required()
                                    ->maxLength(255),
                                   });
                    }),
            ];
        );