Magento 2 – How to Position Custom Tab in Customer Edit Page in Admin Panel

So my understanding is you want to add a grid to the product edit/ new product page.

First thing you will need to do is add a adminhtml XML file to you modules config.xml if it does not allready have one.

in etc/config.xml

 <adminhtml>
        <layout>
            <updates>
                <theextensionlab_producttab>
                    <file>theextensionlab/producttab.xml</file>
                </theextensionlab_producttab>
            </updates>
        </layout>
    </adminhtml>

The in that layout file add to the reference "product_tabs" we need to call the addTab function as pass in our tabs name and the Block:

<all_products>
    <reference name="product_tabs">
        <action method="addTab"><name>product_sitemap_grid</name><block>theextensionlab_producttab/adminhtml_catalog_product_edit_tab_sitemap</block></action>
    </reference>
</all_products>

<adminhtml_catalog_product_new>
    <update handle="all_products"/>
</adminhtml_catalog_product_new>

<adminhtml_catalog_product_edit>
    <update handle="all_products"/>
</adminhtml_catalog_product_edit>

Note I don't know if there is a handle for new and edit products so I just created a custom handle and created it for both. If you wanted to just have this on all simple products you could have used adminhtml_catalog_product_simple

For our new block to show it needs to implement Mage_Adminhtml_Block_Widget_Tab_Interface and have the functions getTabLabel,getTabTitle,canShowTab,isHidden

For simplicty I have just used the sitemap collection from Magento and copied some of that default code, this is similar to the default grid apart from it implements Mage_Adminhtml_Block_Widget_Tab_Interface.

<?php class TheExtensionLab_ProductTab_Block_Adminhtml_Catalog_Product_Edit_Tab_Sitemap
    extends Mage_Adminhtml_Block_Widget_Grid implements Mage_Adminhtml_Block_Widget_Tab_Interface
{

    //Our tab needs the 4 functions below in order to show on the product page
    public function getTabLabel(){
        return Mage::helper('catalog')->__('Sitemap');
    }

    public function getTabTitle(){
        return Mage::helper('catalog')->__('Sitemap');
    }

public function canShowTab(){
    //Check we have selected a type for our new product
    //If not lets not show the tab
    if($this->getRequest()->getParam( 'type' ) != null
        || $this->getRequest()->getParam( 'id' ) != null){
        return true;
    }
    return false;
}

    public function isHidden(){
        return false;
    }

    public function __construct()
    {
        parent::__construct();
        $this->setId('sitemapGrid');
        $this->setDefaultSort('sitemap_id');
    }

    protected function _prepareCollection()
    {
        $collection = Mage::getModel('sitemap/sitemap')->getCollection();
        /* @var $collection Mage_Sitemap_Model_Mysql4_Sitemap_Collection */
        $this->setCollection($collection);
        return parent::_prepareCollection();
    }

    protected function _prepareColumns()
    {
        $this->addColumn('sitemap_id', array(
            'header'    => Mage::helper('sitemap')->__('ID'),
            'width'     => '50px',
            'index'     => 'sitemap_id'
        ));

        $this->addColumn('sitemap_filename', array(
            'header'    => Mage::helper('sitemap')->__('Filename'),
            'index'     => 'sitemap_filename'
        ));

        $this->addColumn('sitemap_path', array(
            'header'    => Mage::helper('sitemap')->__('Path'),
            'index'     => 'sitemap_path'
        ));

        $this->addColumn('link', array(
            'header'    => Mage::helper('sitemap')->__('Link for Google'),
            'index'     => 'concat(sitemap_path, sitemap_filename)',
            'renderer'  => 'adminhtml/sitemap_grid_renderer_link',
        ));

        $this->addColumn('sitemap_time', array(
            'header'    => Mage::helper('sitemap')->__('Last Time Generated'),
            'width'     => '150px',
            'index'     => 'sitemap_time',
            'type'      => 'datetime',
        ));


        if (!Mage::app()->isSingleStoreMode()) {
            $this->addColumn('store_id', array(
                'header'    => Mage::helper('sitemap')->__('Store View'),
                'index'     => 'store_id',
                'type'      => 'store',
            ));
        }

        $this->addColumn('action', array(
            'header'   => Mage::helper('sitemap')->__('Action'),
            'filter'   => false,
            'sortable' => false,
            'width'    => '100',
            'renderer' => 'adminhtml/sitemap_grid_renderer_action'
        ));

        return parent::_prepareColumns();
    }

}

You will then see in this case the sitemap in a grid on your product edit page or in your case your custom grid.

<codepPool> should be <codePool>. You can turn on the system logs in the admin panel -> System -> Configuration -> ADVANCED -> Developer -> Log Settings -> Enabled : Yes. After this you can check them in var/log.