What is diffrents between Portfolio & Work History and Feedback? When you fill out the form portfolio, it prompts you to select items from a work history? Is it possible to complete the portfolio from linkedin?
Work History and Feedback is the section of a freelancer profile in which freelancer's contracts are shown, together with the feedback and ratings they receive from their clients and their own feedback.
Freelancers have the option to link their contracts to their Portfolio and showcase the work they've delivered to their clients on Upwork (with clients' permission). That's why you're seeing an option to select one of your past contact from the list when adding samples to your portfolio.
I can confirm Preston's reply that you can't complete your Upwork Portfolio from your LinkedIn profile.