I found the ability to have multiple columns in a paragraph text element in ArcMap to be invaluable. It seems to be an obscure capability but essentially it allows wrapping the contents of a polygon text element to fit text better. The normal functionality of a polygon text element is to chop off any text that does not fit in a single column.
ArcGIS Pro does not have the columns and margins option on polygon text elements. Personally, the use case for this is when utilizing custom code to populate the text boxes with lots of data for many different contexts (Like datadriven pages). Having the number of columns attribute allows you precise control over how the text is displayed.
The alternative to this is creating multiple text boxes and calculating the shape to determine when its full, and then proceeding to populate a secondary text box, not very efficient.
Please bring back columns and margins to polygon text elements. If this gets implemented, please expose this functionality in the Pro SDK as well, just as it is in ArcObjects.