Some other Wikimedia sites have a gadget which makes it possible to display dynamic watchlist messages (above the actual content of the watchlist).
Wikidata currently displays a static content there, which is updated mostly manually by admins. This content is often stale, takes a lot of space on small screens, and users have no simple way to hide it once they have read it.
Enwiki has two gadgets (watchlist messages and geonotices) which adds a button enabling users to dismiss messages displayed there. Commonswiki has one gadget (called WatchlistMessages) which merges the functionality of both gadgets into one gadget (which allows the community to advertise particular events to a very narrow geographical audience). Other wikis probably have similar gadgets.
The template used by enwiki's gadget already exists in Wikidata but is not functional without the gadget (the dismiss button will not appear, even if the message is rendered in the watchlist).
Therefore I request the activation of such a gadget (probably the one from commons as it looks more advanced) in Wikidata. After a trial period we probably want to consider enabling it by default given that the code is already well tested in sister projects (where it is also enabled by default).
The move was discussed on wiki:
This move requires both the activation of one of these gadgets and also changes in the messages themselves. The migration to the relevant templates can be done first: although users will not be able to dismiss the messages, they will still expire by themselves after a set delay.