You can add extra columns to any Row layer in your email by clicking on the Row layer in Figma, and then adding a new empty Column layer to it via the Quick Add Element dropdown selector at the bottom of the plugin window.

This will add a brand new empty Column which you can then start populating with content layers (eg. text, images, buttons, etc) and customizing the layerโ€™s styles (eg. changing the background color, adjusting padding and spacing, etc) in Figma as needed.

Please note that each Row can only have a single row of Columns, so youโ€™ll need to create a brand new Row whenever you decide to have a different number of columns as a underneath your existing row of columns.
๐Ÿ›๏ธ Column elements can only be added directly inside of ๐Ÿšฃ Row layers. If you need multiple rows of columns, youโ€™ll need to create brand new ๐Ÿšฃ Row for each row of columns you need.