Magento2 – Which Entity Allows Scoped Attributes?

• customer and customer_address Does not support Scope Attribute [Global]
• catalog_category and catalog_product Does support Scope Attribute [Default, Website and Store]

So the question is, Sales tables does support Scope Attributes? Because sales tables are stored as Flat tables in Magento

Sales DOES NOT support Scope Attributes.

Confirmation 1 : Check the eav_entity_type table in Magento 2

• attribute_model and entity_attribute_collection is NULL for sales related entities.
• Where as Customer Attributes can be created Scope wise.
• Catalog Attributes can be created Scope wise.

Confirmation 2 : Check getDefaultEntities function in Setup folder, It clears the doubt.

vendor/magento/module-customer/Setup/CustomerSetup.php

/**
     * Retrieve default entities: customer, customer_address
     *
     * @return array
     * @SuppressWarnings(PHPMD.ExcessiveMethodLength)
     */
    public function getDefaultEntities()
    {
        $entities = [
            'customer' => [
                'entity_type_id' => \Magento\Customer\Api\CustomerMetadataInterface::ATTRIBUTE_SET_ID_CUSTOMER,
                'entity_model' => \Magento\Customer\Model\ResourceModel\Customer::class,
                'attribute_model' => \Magento\Customer\Model\Attribute::class,
                'table' => 'customer_entity',
                'increment_model' => \Magento\Eav\Model\Entity\Increment\NumericValue::class,
                'additional_attribute_table' => 'customer_eav_attribute',
                'entity_attribute_collection' => \Magento\Customer\Model\ResourceModel\Attribute\Collection::class,
                'attributes' => [
                    'website_id' => [
                        'type' => 'static',
                        'label' => 'Associate to Website',
                        'input' => 'select',
                        'source' => \Magento\Customer\Model\Customer\Attribute\Source\Website::class,
                        'backend' => \Magento\Customer\Model\Customer\Attribute\Backend\Website::class,
                        'sort_order' => 10,
                        'position' => 10,
                        'adminhtml_only' => 1,
                    ],
                    'store_id' => [
                        'type' => 'static',
                        'label' => 'Create In',
                        'input' => 'select',
                        'source' => \Magento\Customer\Model\Customer\Attribute\Source\Store::class,
                        'backend' => \Magento\Customer\Model\Customer\Attribute\Backend\Store::class,
                        'sort_order' => 20,
                        'visible' => false,
                        'adminhtml_only' => 1,
                    ],

vendor/magento/module-catalog/Setup/CategorySetup.php

/**
     * Default entities and attributes
     *
     * @return array
     * @SuppressWarnings(PHPMD.ExcessiveMethodLength)
     */
    public function getDefaultEntities()
    {
        return [
            'catalog_category' => [
                'entity_type_id' => self::CATEGORY_ENTITY_TYPE_ID,
                'entity_model' => Category::class,
                'attribute_model' => Attribute::class,
                'table' => 'catalog_category_entity',
                'additional_attribute_table' => 'catalog_eav_attribute',
                'entity_attribute_collection' =>
                    Collection::class,
                'attributes' => [
                    'name' => [
                        'type' => 'varchar',
                        'label' => 'Name',
                        'input' => 'text',
                        'sort_order' => 1,
                        'global' => ScopedAttributeInterface::SCOPE_STORE,
                        'group' => 'General Information',
                    ],

vendor/magento/module-sales/Setup/SalesSetup.php

/**
     * @return array
     */
    public function getDefaultEntities()
    {
        $entities = [
            'order' => [
                'entity_type_id' => self::ORDER_ENTITY_TYPE_ID,
                'entity_model' => \Magento\Sales\Model\ResourceModel\Order::class,
                'table' => 'sales_order',
                'increment_model' => \Magento\Eav\Model\Entity\Increment\NumericValue::class,
                'increment_per_store' => true,
                'attributes' => [],
            ],
            'invoice' => [
                'entity_type_id' => self::INVOICE_PRODUCT_ENTITY_TYPE_ID,
                'entity_model' => \Magento\Sales\Model\ResourceModel\Order\Invoice::class,
                'table' => 'sales_invoice',
                'increment_model' => \Magento\Eav\Model\Entity\Increment\NumericValue::class,
                'increment_per_store' => true,
                'attributes' => [],
            ],
            'creditmemo' => [
                'entity_type_id' => self::CREDITMEMO_PRODUCT_ENTITY_TYPE_ID,
                'entity_model' => \Magento\Sales\Model\ResourceModel\Order\Creditmemo::class,
                'table' => 'sales_creditmemo',
                'increment_model' => \Magento\Eav\Model\Entity\Increment\NumericValue::class,
                'increment_per_store' => true,
                'attributes' => [],
            ],
            'shipment' => [
                'entity_type_id' => self::SHIPMENT_PRODUCT_ENTITY_TYPE_ID,
                'entity_model' => \Magento\Sales\Model\ResourceModel\Order\Shipment::class,
                'table' => 'sales_shipment',
                'increment_model' => \Magento\Eav\Model\Entity\Increment\NumericValue::class,
                'increment_per_store' => true,
                'attributes' => [],
            ],
        ];
        return $entities;
    }

In Conformation 2 - getDefaultEntities is Scope wise for Customer Attributes and Catalog as well Categories But Sales DOES NOT support Scope Attributes, It is not defined in Setup.