При создании связки создается ui, но не возвращает значение id.
Model test:
class test extends Model
{
    use HasFactory;
    protected $guarded = [];
    public function ui_name() {
        return $this->belongsTo('App\Models\Uis', 'name_id', 'id');
    }
    public function ui_desc() {
        return $this->belongsTo('App\Models\Uis', 'desc_id', 'id');
    }
}
UI Model:
class Uis extends Model
{
    use HasFactory;
    protected $guarded = [];
    public function category() {
        return $this->hasOne('App\Models\Categories\Category', 'ui_id', 'id');
    }
    public function tag() {
        return $this->hasOne('App\Models\Tags\Tag', 'ui_id', 'id');
    }
    public function test_name() {
        return $this->hasOne('App\Models\Tests\test', 'name_id', 'id');
    }
    public function test_desc() {
        return $this->hasOne('App\Models\Tests\test', 'desc_id', 'id');
    }
}
Controller:
$test = new test();
        $test->ui_name()->create([
            'text' => "TEXT",
            'desc'=> "TEXT",
            'module_id' =>1, 
            'isHTML' => false
        ]);
tests table:
Schema::create('tests', function (Blueprint $table) {
            $table->id();
            $table->bigInteger('name_id');
            $table->bigInteger('desc_id')->nullable();
            $table->integer('max_ball')->default(20);
            $table->string('password')->nullable();
            $table->string('special_link')->unique()->nullable();
            $table->timestamps();
        });
uis table:
$table->id();
            $table->string('text');
            $table->text('desc');
            $table->bigInteger('module_id')->nullable();
            $table->boolean('isHTML')->default(false);
            $table->timestamps();
Warning:
ErrorException
Trying to get property 'id' of non-object