to get the structure of the of the new elements to fit the design, you should copy an existing line group and add the select list to the new line.
It's not 100% necessary, but it does preserve the forms design.
once you have a div in place for the select list, add a spry select list, and a recordset to return the available group levels.
select the list in design view, then in the property inspector, click the dynamic button to set the list to populate from the recordset.
once the list is in place, you can edit the server validation behavior to add validation, and add the validation show if.