gistfile1.txt

class ShipmentHandlingUnitsTable extends Table
{....
    public function initialize(array $config)
    {
        ...
        
        $this->belongsToMany('OrderLines', [
            'foreignKey' => 'shipment_handling_unit_id',
            'targetForeignKey' => 'order_line_id',
            'joinTable' => 'order_lines_shipment_handling_units'
        ]);
    }

-------------
    
class ShipmentsTable extends Table
{
  ...
    public function initialize(array $config)
    {
      ...
        $this->hasMany('ShipmentHandlingUnits', [
            'foreignKey' => 'shipment_id'
        ]);
    }
    
    
-------

 $shipment = $this->Shipments->patchEntity($shipment, $this->request->getData(),['associated'=>['ShipmentHandlingUnits.OrderLines']]);
 
 
----

echo $this->Form->input("shipment_handling_units[0].order_lines[$i]._joinData.order_line_id",['type'=>'hidden','value'=>$orderLine->id]);
echo $this->Form->input("shipment_handling_units[0].order_lines[$i]._joinData.qty",['label'=>'']);