I think it is good to add more filter like
* Item types (such as issue, pull request and etc …)
* Item status for each type of item (for example for issue type: open issue, closed issue and etc …)
as well as add search bar to this section (like search bar in issues page with advanced directive).
All above tools help all developers that have many (more than 50 subscriptions per repository) subscriptions to manage it and more and easy contribute to it.