Hi Martin,
Thank you for reaching out with your BoldGrid Post and Page Builder questions! Since there’s no actual way to split a section in Post and Page Builder, I think the simplest way to accomplish this would be to duplicate the current section layout and save it as a new “Block Template”. In this template add new rows for your text in above and below the image and save the new template block. Here’s a guide on working with rows in Post and Page Builder.
You’ll have two separate template blocks for each situation. This makes it easy to add in your new content without creating new columns and rows on the fly.
I hope this helps.