Dokan Pro 2.6.7 update already rolled out along some advanced features with it. Social API is one of them which will let your users register/login to your multi-vendor marketplace using their social profiles like Facebook, Twitter, Google Plus and LinkedIn.
Configuration & Settings
To configure Social API on your Dokan, Please login to your WordPress dashboard and navigate to Wp-admin→ Dokan→ Settings→ Social API and Checkmark(√) the indicated option below to Enable Social Login
Enabling Social Login will add the social icons under the registration form and users will be able to log in or register using their social profiles by clicking those icons. It will be shown as below: