<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:DataObject/etc/fieldset.xsd">
    <scope id="global">
        <fieldset id="extra_checkout_billing_address_fields">
            <field name="bl_flat_number">
                <aspect name="to_order_address" />
                <aspect name="to_customer_address" />
            </field>
            <field name="map_link">
                <aspect name="to_order_address" />
                <aspect name="to_customer_address" />
            </field>
        </fieldset>
        <fieldset id="extra_checkout_shipping_address_fields">
            <field name="bl_flat_number">
                <aspect name="to_order_address" />
                <aspect name="to_customer_address" />
            </field> 
            <field name="map_link">
                <aspect name="to_order_address" />
                <aspect name="to_customer_address" />
            </field>
        </fieldset>
        <fieldset id="sales_convert_quote_address">
            <field name="bl_flat_number">
                <aspect name="to_customer_address" />
                <aspect name="to_order_address" />
            </field>
            <field name="map_link">
                <aspect name="to_customer_address" />
                <aspect name="to_order_address" />
            </field>
        </fieldset>
        <fieldset id="order_address">
            <field name="bl_flat_number">
                <aspect name="to_customer_address" />
            </field>
            <field name="map_link">
                <aspect name="to_customer_address" />
            </field>
        </fieldset>
    </scope>
</config>