Magento 1.8 – Fix Disappearing Newsletter Tab in Admin Backend After Upgrade

Looks like you don't have permissions for your admin user. Try to delete the cookies for that domain to get a new php session.

Or recreate the tables for admin users/roles. Have a clean install of Magento 1.8 and import those clean good tables. Do this on a test/developing server first. And backup the database and code first of all, even if it's a test server.

So it turns out that app/code/core/Mage/Adminhtml/Block/Catalog/Product/Edit/Tabs.php is the correct file. I or someone else had copied it to the local directory so that copy was being used instead. Moving the categories tab above the inventory tab via manipulating their order in the code did work. I was also able to follow this guide:

http://www.netismine.com/magento/change-tab-order-in-product-admin

To hide my Additional Fields tab, then copy the code and reinclude the tab beneath the Categories tab, so that Categories appeared second. I also commented out the Up-sells etc tabs as I have no use of them.

If it helps, here is the code from the edits.php tab down to the Inventory tab:

protected function _prepareLayout()
{
    $product = $this->getProduct();

    if (!($setId = $product->getAttributeSetId())) {
        $setId = $this->getRequest()->getParam('set', null);
    }

    if ($setId) {
        $groupCollection = Mage::getResourceModel('eav/entity_attribute_group_collection')
            ->setAttributeSetFilter($setId)
            ->setSortOrder()
           ->addFieldToFilter('attribute_group_id',array('nin'=>array('27'))) // using 'in' instead of 'nin' will only return these tabs
            ->load();

        foreach ($groupCollection as $group) {
            $attributes = $product->getAttributes($group->getId(), true);
            // do not add groups without attributes

            foreach ($attributes as $key => $attribute) {
                if( !$attribute->getIsVisible() ) {
                    unset($attributes[$key]);
                }
            }

            if (count($attributes)==0) {
                continue;
            }

            $this->addTab('group_'.$group->getId(), array(
                'label'     => Mage::helper('catalog')->__($group->getAttributeGroupName()),
                'content'   => $this->_translateHtml($this->getLayout()->createBlock($this->getAttributeTabBlock(),
                    'adminhtml.catalog.product.edit.tab.attributes')->setGroup($group)
                        ->setGroupAttributes($attributes)
                        ->toHtml()),
            ));
        }

        $this->addTab('categories', array(
            'label'     => Mage::helper('catalog')->__('Categories'),
            'url'       => $this->getUrl('*/*/categories', array('_current' => true)),
            'class'     => 'ajax',
        ));

        $groupCollection = Mage::getResourceModel('eav/entity_attribute_group_collection')
            ->setAttributeSetFilter($setId)
            ->setSortOrder()
           ->addFieldToFilter('attribute_group_id',array('in'=>array('27'))) // using nin hides that tab id
            ->load();

        foreach ($groupCollection as $group) {
            $attributes = $product->getAttributes($group->getId(), true);
            // do not add groups without attributes

            foreach ($attributes as $key => $attribute) {
                if( !$attribute->getIsVisible() ) {
                    unset($attributes[$key]);
                }
            }

            if (count($attributes)==0) {
                continue;
            }

            $this->addTab('group_'.$group->getId(), array(
                'label'     => Mage::helper('catalog')->__($group->getAttributeGroupName()),
                'content'   => $this->_translateHtml($this->getLayout()->createBlock($this->getAttributeTabBlock(),
                    'adminhtml.catalog.product.edit.tab.attributes')->setGroup($group)
                        ->setGroupAttributes($attributes)
                        ->toHtml()),
            ));
        }

        $groupCollection = Mage::getResourceModel('eav/entity_attribute_group_collection')
            ->setAttributeSetFilter($setId)
            ->setSortOrder()
           ->addFieldToFilter('attribute_group_id',array('in'=>array('27'))) // using 'in' only returns this tab ID
            ->load();

        if (Mage::helper('core')->isModuleEnabled('Mage_CatalogInventory')) {
            $this->addTab('inventory', array(
                'label'     => Mage::helper('catalog')->__('Inventory'),
                'content'   => $this->_translateHtml($this->getLayout()
                    ->createBlock('adminhtml/catalog_product_edit_tab_inventory')->toHtml()),
            ));
        }