In Magento 2 Marketplace Multi-Vendor module, the admin can restrict the sellers from configuring their Shipping & Return policy.
For this, the admin will navigate to Stores > Configuration > Webkul > Marketplace > Seller Profile Page Settings.
Under the Seller Profile, Page Settings section set the Sellers Policies Enable at Frontend field as “No”.
This way the sellers can’t view the Shipping and Return Policy fields on the seller profile page. Therefore, the sellers will longer be able to define it.