To clearly distinguish “normal text” in a score from the name of the role/group to sing a certain voice, I have been using expression enclosures back when I was working with finale:
Using expressions still seems to be a good option in Dorico because I can globally update the styles if needed, but I don’t find a way to add an enclosure such as the rectangle in the screenshot.
What are you using specifically in Dorico that you think of as “expressions”? Are you using dynamics, or playing techniques, or just plain Shift+X text?
Unfortunately at the present time it’s not easy to enclose a playing technique in a box like your picture shows. If you want to use a border like this, you’ll need to use Shift+X text and a suitably defined paragraph style.
Just to add, if you use a paragraph style, if you decide to change font/formatting etc, changing the paragraph style will update all of the instances of it in your project…