I’ve got a feeling @jags would like to assign custom fields to the Posts list page itself as its own entity and I’m pretty sure that’s not possible. However, I think what you could do is customise the in-built filter to achieve the same result.
https://wordpress.stackexchange.com/questions/16637/how-to-filter-post-listing-in-wp-dashboard-posts-listing-using-a-custom-field/16641
