Thread:Extension talk:Semantic Forms Inputs/Sort order for "two listboxes"?/reply

I think it should be possible to do that using the plain "values" parameter (i.e. not one of the "values from..." parameters). You could try using an ask query, something like. Of course you then face the problem of sorting that ask.

If you already specify allowed values with your properties the simplest solution might be to just explicitly list the allowed values by hand in your form. Or - if you have many forms - to put the list of allowed values in a template. All not very comfortable or elegant, I know.