Select Field in external form does not show value from process

Hi all!

I have an select form field in first external html form and I want so have the same field in the second form, but with selected value from first form.

 <select cam-variable-name="verbuchung" cam-variable-type="String" class="form-control" id="verbuchung" required="" type="">
     <option value="unbekannt">
     <option value="Allgemeinkosten">
     <option value="Toolkostenumlage">
     <option value="direkte Projektverrechung">
      direkte Projektverrechung

But in the second form no one value ist selected. The value is stored in process variables.

What to do?

Best Regards,

Is there no possibilty to set select field in an external form on value of a former set process variable?