I really can’t think of a way to automate this.
But here are some options:
If you are rebreaking those other lines for aesthetic reasons, have you considered using the “no break” feature? I normally set up a “no break” character style sheet so I can force lines down to the next line without having to use soft returns. I simply highlight the words and spaces that I want to move down, and apply the “no break” character style.
Or, you would have to set up a second paragraph style sheet where’s nested to be bold through two soft returns. Then when you are breaking the lines for aesthetic reasons, you can simply click the other paragraph style.
I have gotten in the habit of using the “no break,” however, mainly because of chapter titles and running heads. InDesign doesn’t like it when a soft return is used, and will add a space at the end of the runninghead. So I use “no break” to force lines down. Also–when we convert books to ebooks, it alleviates us having to go in and strip out the soft returns.