This shortcode shows the display name of the currently logged-in user, based on your configuration inside ProfileGrid Display Name Extension. (If the extension is not installed, it will show the full name of the user. If the First Name is not set, it will show Display Name.) To publish the display name of another user, use the uid parameter.
[profilegrid_user_display_name uid="1"] uid is a user ID and its optional The shortcode is available with the ProfileGrid User Activities Extension.