Is it possible to use the extended character set from Petaluma for things like putting nice custom borders around text similar to how you can with the JazzFont in Finale? I can’t seem to figure out how to get them into a text item. Furthermore, they don’t seem to have assigned unicode values.
Welcome to the forum, Erik. Unfortunately at the moment it’s not possible to use those borders in Dorico because they require the selection of a specific stylistic set from within the font, which is something that the underlying Qt framework Dorico relies upon cannot do. I hope to come up with a solution for this in future, one way or another, but I’m afraid there’s no way to do this at the moment directly within Dorico.
You can put borders around text objects graphically, rather than using font characters (so 80s! 
). It might be too square for Jazz, of course.