Hey Bkimani,
If your question is just about adding a 'sort' capability based on the Rank to a normal list where people are managing stories, projects, tasks etc., whether in a workspace or older 'list' view, the sort functionality should be as straightforward as exposing the 'rank' field in the list view, and allowing the users to click the header to sort the data.
However, if you'll forgive me being a bit nosey, I'm really interested in why you've done this. You're attempting to mirror functionality that is already available in the SPW. You've clearly got SPM licensing if your users are working with planning items, so why aren't those users accessing the SPW for their planning needs? Is there something specific they need that's not provided that you're capturing in your own view, or are you aiming to show this field to users who only have Scrum User?
