_handleSendToSource() {
    const itemsToSend = [];
    this._dataTarget.forEach((item) => {
      if (item.checked) {
        itemsToSend.push(item);
      }
    });
    !!!!!EventHandler.trigger(this._element, EVENT_ON_CHANGE, { sentItems: itemsToSend });
    !!!!!console.log('trigger change1');

    this._dataTarget = this._dataTarget.filter((item) => {
      const isNotCheck = !item.checked;
      item.checked = false;
      return isNotCheck;
    });
    this._dataSource = [...this._dataSource, ...itemsToSend];

    >>>>>EventHandler.trigger(this._element, EVENT_ON_CHANGE, { sentItems: itemsToSend });
    >>>>>console.log('trigger change1');
  }

Thank you for the documentation, there is a big unsolved issue .

I cannot retrieve datasource and datatarget after the onChange.

the onChange handlers triggers before change, so we need a handler after change of lists.

Am I right or wrong ?

Hello, thank you for your feedback. We will fix this asap.