In the default WooCommerce Marketplace, there is no option to extend the registration form of the seller. However, if you want to integrate this feature into your Marketplace then you can install the Marketplace add-on Marketplace Custom Registration for WordPress WooCommerce.
This plugin allows the admin to create the vendor’s custom attributes. Vendors can fill the attributes registering to the marketplace.
Please do contact us for any further queries or requirements. You can also check our Woocommerce Extensions for additional features.