Hello!
Is there a feature to have the tenuto written as expression text (preferably ten.) instead of as a music symbol, as in the attached example? Or will I have to use the text function?
I’m not sure this is “baked in” yet (I could be wrong) but you can accomplish this very easily using shift-X and typing “ten.”
Yes, that’s the way I’m doing it right now, and it works pretty well of course. 
Hello. Does @Romanos advice for entering ten. as text instead of a symbol still stand? Tenuto (ten.) for a singer really does mean ‘held’, in my experience and could perhaps be added to playing techniques for singers.
You could create it as a custom playing technique, if you like.