I've seen a few ideas supporting this same request, but both requests were more than a decade old.
What I think would be brilliant is the ability to easily format text in Pro in the same way that we are able to do in common software programs like Microsoft Office, where you highlight the portion of the text you want to format and then click buttons, rather than try to add properly formatted tags.
I've spent over an hour trying to track down the proper tags for a multi-line, multi-font label in ArcGIS Pro. Multiple unhelpful Google searches later I finally found the right tags and formatting, but new issues with the labels suddenly surfaced. I'm not a programmer or a coder. It's frustrating to spend so much time trying to get tags just right and in the right order to make a label.