Twitter has said it will close Dashboard (Beta) on February 3, 2017, but it's not said much more. I wonder if it has been trying to run too many different apps. The best of this beta app might surface in others, such as tweetdeck.
From there, the idea being you could schedule tweets, run searches, and see analytics. The first two were already in tweetdeck, and available in other third party tools. Analytics, of course, are also available here [analytics.twitter.com...]
It's a shame it wasn't developed further as it would have helped bring more of the fragmented tools and facilities into one dashboard.