You can manually add a product review in Magento 2 backend by following these steps:

• Log in to your Magento 2 Admin Panel.
• Navigate to Marketing → User Content → All Reviews.
• Click Add New Review.
• Select the product you want to add the review for.
• Fill in the reviewer details, star rating, and review content.
• Set the status to Approved and click Save Review.

With the Magento 2 Advanced Product Reviews Extension, you get enhanced admin control to manage, filter, and respond to all reviews from a single dashboard.