Right now, the only option in Special:EditWatchlist is removing a page completely from a user watchlist. Furthermore, I found de-watching and then re-watching a page (i.e. clicking a full blue star, re-clicking a star and then converting it to a half-star) just to set (or extend) expiry time more annoying. Have adding time expiry settings to "Special:EditWatchlist" been considered yet? That would make "Special:EditWatchlist" easier to use.
By the way, this applies to desktop view and advanced mobile view. I wouldn't extend this request to normal mobile view yet.