I see from the AI scan that others have brought this up in the past, but just to confirm: the ‘short trill’ is what otherwise would be called (by some) an upper mordent, and the slashed symbol identfied as ‘mordent’ corresponds to the lower mordent?
I was disappointed to find that, when trying to solve this through playback, they didn’t play back as ornaments at all. This, in the past, has been slated for future implementation – what is the current situation?
I guess one of the main problems in implementing such a feature would be the large stylistic differences that exist in the performance of such ornaments. A mordent means something entirely different in, say, Rameau and Rachmaninoff. Finale used to solve this, somewhat, by letting the user choose from different playback styles. But that was far from ideal as well.
We do plan to implement playback of ornaments in a future version, but at the moment I can’t say when that might be.
Can you explain the difference between a Rameau and a Rakhmaninov mordent?
Hi, in Dorico 5 it seems still not implemented. It’s really a missing feature, even if not automatic, at least it could let us personalize each mordent.
If useful, see also 'short trill' (ornament popover input: shorttr) is ignored when playing score - #11 by Alberto_Maria
Any update about when this might be included? Thanks!
The Team usually does not give any information about the features that will be implemented in the next update. Nor when that update will happen. Sometimes, Daniel leaks some information, usually very few days before the update is out, when the beta testing has already shown that it won’t cause problems. So I suggest you stick to the existing methods for having those ornaments play the way you want, or be prepared to wait for a loooooong time 
I am a previous Finale user, who was told that Dorico is the future. This is disappointing that simple mordent is not played back. Why is it such a big problem for Dorico, which old Finale had no problem with?
Because they can’t give everybody everything all at once. The modernists want cutaway scores, the lutenists want lute tablature, the editors want parentheses round everything, and there’s a 1000 other “simple” things that people want.
Also, start a thread here about “how should a mordent be played?”, and you’ll get as many different answers as you can eat.
If past performance is any guarantee (such as Dorico’s playback of fermatas and caesuras), you can rest assured that when ornament is implemented, it will do everything you need – and possibly more!
In the meantime you can use the workaround that works exactly the way you want : add a staff above or below (right-click>Staves>Add staff…), write exactly what you want to hear (with notes and rhythms) and make sure you set the property of the note with the mordent to suppress playback. You can now delete the added staff, the nores should still play (I know, it’s tricky but convenient…)
By the way, some libraries have mordents. E.g., VSL Studio Woodwind flute, and you can create a custom playback to use with it.