For anybody writing music a list of terms would be very useful indeed.
Sibelius has a few, but not nearly enough - so you go to the tempo text option and click on "allegro" for example and allegro comes up where you want it.
I still do my initial scores on Notation Composer because I find it easier and more intuitive than Sibelius (which I use only to tidy up a professional standard score and parts).
When I add Italian terms as free text I find myself having to double check the spelling on the internet. A bank of terms would avoid this. Also it's a great educational resource to have these terms incorporated into Notation Composer.
I know you are concentrating on marketing the product right now, but I think this is a product feature which would be quite easy to add and a way of keeping long time users happy - to see the product still developing.