Magento – UI: Backend Catalog -> Manage Products -> edit product (Related Products, Up-Sells, Cross-Sells)

On the webguys page is a german article about this problem: http://www.webguys.de/magento/turchen-23-pimp-my-produktgrid/

Nicht alle unsere Änderungen werden von Magento übernommen, zum Beispiel funktioniert die Sortierung und Filterung der neuen Attribute nicht.

Das liegt daran, dass unsere Änderungen nach dem Aufruf von _prepareCollection(), in dem die Spalteninfos an die Collection übergeben werden, stattfinden.

Translation:

Not all changes are made by magento, e.g. sorting and filtering of the new attributes doesn't work.

That's because they are made after the _prepareCollection() call, where the informations about the columns are passed to the collection.

protected function _callProtectedMethod($object, $methodName) {
    $reflection = new ReflectionClass($object);
    $method = $reflection->getMethod($methodName);
    $method->setAccessible(true);
    return $method->invoke($object);
}

protected function _modifyProductGrid(Mage_Adminhtml_Block_Catalog_Product_Grid $grid) {
 
    $this->_addUpdatedAtColumn($grid);
    $this->_addColorColumn($grid);
 
    $this->_removeColumn($grid, 'set_name');
    $this->_removeColumn($grid, 'visibility');       

    // reinitialisiert die Spaltensortierung
    $grid->sortColumnsByOrder();
    // reinitialisiert die Sortierung und Filter der Collection
    $this->_callProtectedMethod($grid, '_prepareCollection');               

} 

More in the post. I think the source code is quite self explaining and if not, use google (if you don't understand german ;-))

You can do that via the menu Catalog > Attributes > Manage Attributes and creating an attribute with a Dropdown type.

After that, you can add it to the attribute set of your choice in Catalog > Attributes > Manage Attribute Sets. Select your Set, then drag your attribute in the right column, and drop it in the left one, under the group "Images". Your attribute should then display in "Manage Products".

If you want to add this attribute programmatically, you can do it with an installer, and a code like that :

<?php
$installer = $this;

$installer->startSetup();

// Group : General
$attributeSetDefault = 'Default';
$attributeGroup = 'Images';
$attributeSetId = $installer->getAttributeSetId('catalog_product', $attributeSetDefault);
if($attributeSetId){
    $attributeGroupId = $installer->getAttributeGroupId('catalog_product', $attributeSetId, $attributeGroup);
}

// Attribute : attribute_code
$attributeCode = 'attribute_code';
$attribute = $installer->getAttribute('catalog_product', $attributeCode);
if (empty($attribute['attribute_id'])) {

    $options = array();
    $options['value']['option0'][0] = 'Option 0';
    $options['value']['option1'][0] = 'Option 1';

    $installer->addAttribute(
        'catalog_product',
        $attributeCode,
        array(
            'label'                         => 'Attribute',
            'type'                          => 'varchar',
            'backend'                       => 'eav/entity_attribute_backend_array',
            'frontend'                      => '',
            'input'                         => 'select',
            'frontend_class'                => '',
            'source'                        => '',
            'required'                      => false,
            'user_defined'                  => true,
            'default'                       => '',
            'unique'                        => false,
            'global'                        => Mage_Catalog_Model_Resource_Eav_Attribute::SCOPE_GLOBAL,
            'option'                        => $options,
        )
    );

    $attributeId = $installer->getAttributeId('catalog_product', $attributeCode);

    if($attributeGroupId && $attributeId){
        $installer->addAttributeToGroup('catalog_product', $attributeSetId, $attributeGroupId, $attributeId);
    }
}


$installer->endSetup();