The top 9 Magento B2B professional extensions of 2023, according to the 2021 research by Magestore, include the Minimum Order Quantity Extension, the Product Question Extension, and the B2B Registration Form Extension. Other popular options include the Wholesale Features Extension, the B2B Marketplace Solution, and the B2B Solution for Magento. These extensions offer crucial features such as advanced pricing options, access restrictions, and personalized marketing, making them indispensable for B2B projects.