Groove finally added a form of search to their product. In the latest beta release one can search in a (single) discussiontool and all of your messages using Ctrl-F.

Many people have been waiting for this for a long, long time and the lack of any search has frustrated a lot Groove users including myself over the past years. Although there is still a lot of room for improvement before Groove has proper search functionality, it's very encouraging to see that Groove has finally started to adress this !!!