It would be nice if via some keyword, a dashboard specification could request that a given pane be hidden when the search is empty, e.g.
Has+Draft+Comments=hide-empty+has:draft+-age:3w
If there are no drafts on recently active reviews, then instead of a pane showing "No Changes", the pane completely disappears due to this 'hide-empty" keyword.
Currently if you want this, you have to hack it on the client side with user scripts or whatever.