In Magento 2 Multi-Vendor Marketplace module when the admin needs to assign any product or mass assign products to any particular seller, the admin will click the menu item “Product Assignment” under Marketplace Management > Manage Seller > Select seller for the product assignment and go to the Product Assignment tab.
Here the admin will find a complete list of all the products in the catalog.
The admin will check the Ids of the products that are to be assigned to the seller and will click on the save customer button in order to assign products to the seller.
Please do contact us for any further queries or requirements. You can also check our Magento 2 Extensions for additional features.