Keep with Next for title options

I am experimenting with export formats.
I have a format that exports the title and also has the title options, Title prefix of <$parenttitle>:
There is a carriage return after the <$parenttitle>: so that it appears on a separate line … above the title.
This works fine :slight_smile:

However, there are some occasions where that calculated text of <$parenttitle>: appears at the bottom of a page while the section’s title (and text!) appears on the following page.

How do I apply ‘keep with next’ to the Title prefix?