I couldn't find this in any product documentation but I was wondering it's possible when using categories in a grid, if we could designate that it only display the category set as primary in wordpress?
Welcome to our forum.
you can display default categories and tags under the grid, but you can't display custom taxonomies and terms, this is only available in pro version.
In WordPress there is a primary category feature available, it might be coming from 3rd party plugins. we don't have any elements to show primary category.