It’s not really possible to insert formatted text from one document to another in small fragments, it is only possible in sections.
At the moment you can only insert inline images, that means the text will not wrap around it, unless you arrange the image and the text in cells of a table so the text will be properly positioned around the image. We will later add options to insert image with different positioning and wrapping options. This will be one of the minor releases in 1-2 month.
If you move into a cell using DocumentBuilder, I don’t think it is possible to insert extra cells and change existing cell borders, but it’s a good idea and I will add it to the task list.