expand sentence to paragraph instead of expanding ten words into hundreds.

I’m going to create a plugin for this but it ought to be a feature. Typically, I only want to expand a sentence into a paragraph. The way expand currently works, it tries to tell the entire story instead of just expanding the part of the story I want expanded. For example, if I want to expand the sentence “Bob entered the room” I want it to expand Bob entering the room and not add anything about Bob walking through the park a week later.