Create an extension attribute on Magento\Seles\Api\Data\OrderInterface and an after plugin on Magento\Sales\Model\Order: :getExtensionAttributes() to add the custom data.

Create a before plugin on Magento\Sales\Model\ResourceMode\Order\Collection:: load and alter the query to fetch the additional data. Data will then be automatically added to the items fetched from the API.

Create an extension attribute on Magento\Sales\ApI\Data\Orderinterface and an after plugin on Magento\sales\Api\orderRespositoryinterface on get() and getlist () to add the custom data.

Option A

Option B

Option C

Create an observer that listens to the adminhtml_config_system_save_after

Add a new field in etc.adminhtml/system.xml in my_Module with the file type:

Add a custom backend model which extends /Magento\Framework\App\Config\Value and call afterSave:

Add a new field in etc/adminhtml\system.xml in My_Module with a new custom type: