Take the secondary actions of cities and regions as an example, when I select Shenyang, the regional list becomes Peace Zone, Shenhe Zone, Tiexi Zone, etc. When I select Dalian, it shows Wafangdian, Ganjingzi, etc.

First, follow laravel-admin's documentation and add it to Model

    public function __construct(array $attributes = [])
    {
        parent::__construct($attributes);

        $this->setParentColumn('pid');
        $this->setOrderColumn('sort');
        $this->setTitleColumn('name');
    }

Then add a select control for the city and region on the form

    protected function form()
    {
        return Admin::form(AreaModel::class, function (Form $form) {

            $form->text('name', 'Name')->rules("required");
            $form->select('city_id','City')->options(

                DealCityModel::selectOptionsNoRoot()

            )->load('pid', 'district')->loadOne('pid', 'district');//The load method comes with the framework, defined in the vendor=>encore=>laravel-admin=>src=>Form=>Field=>Select file, the loadone is written by itself, and the code district is given to define the method for itself, and the pid is the name of the drop-down list box that changes depending on the city, which is this one below.

            $form->select('pid','region')->options(array(0 =>'Please select a region'));

        });
    }

Create a new district method after the from method

    public function district(Request $request)
    {
        $cityId = $request->get('q');

        $list = AreaModel::where(['city_id' => $cityId, 'pid' => 0])->get(['id', DB::raw('name as text')]);

        foreach ($list as $key => $value) {

            $arr[] = array("id" => $value->id, "text" => $value->text);

        }

        return $arr;//Returns the option of the array to the region

    }

After the load method in the vendor=>encore=>laravel-admin=>src=>Form=>Field=>Select file, create a new method named loadone with the following code:

    public function loadOne($field, $sourceUrl, $idField = 'id', $textField = 'text')
    {
        if (Str::contains($field, '.')) {
            $field = $this->formatName($field);
            $class = str_replace(['[', ']'], '_', $field);
        } else {
            $class = $field;
        }

        $script = <<<EOT
$(function(){
    var target = $(".$class");
    $.get("$sourceUrl?q="+$("{$this->getElementClassSelector()}").val(), function (data) {
        target.find("option").remove();
        $(target).select2({
            data: $.map(data, function (d) {
                d.id = d.$idField;
                d.text = d.$textField;
                return d;
            })
        });
    });
});
EOT;

        Admin::script($script);

        return $this;
    }

This is equivalent to adding a default data fill to the load method.