At this moment, the workaround that I can suggest is setting the BackgroundImage property with an image of a rectangle to the separate report sections or to the report itself. However, this workaround has a limitation due to that fact that the background image cannot be resized. For that reason, you can set the correct background image size if you know how exactly each section will grow.
In addition, you can log a new feature request for that kind of styling in our Feedback portal.
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