Seems to successfully dynamically create fields on second Screen of a Lift Wizard based on selection in the first Screen. Access fields of the second screen later on using "second.screenFields".

DynamicWizardExample.scala

import net.liftweb._
import http._
import wizard._
import common.{Empty, Box}
import net.liftweb.util.FieldContainer
import model.Thing
 
object ThingsWizard extends Wizard {
 
  val emptyThings: Seq[Thing] = Seq()
  object wizThings extends WizardVar(emptyThings)
 
  val first = new Screen {
    
    val things = multiselect("Some Things", Seq(), Thing.findAll())
 
    override def transitionOutOfTo(to: Box[Screen]) = {
      wizThings(things.is)
    }
  }
 
  val second = new Screen {
    
    // A throw-away screen seems to be required to capture the auto-registration when fields are generated.
    val throwAwayScreen = new Screen {
      def newField(t: Thing) = field(t.description.get, wizThings.is.indexOf(t), minVal(0, "Must be non-negative"))
    }
    
    def newFields() = {
      object NewFields extends FieldContainer {
        def allFields = for( t <- wizThings.is ) yield {
          val thing = throwAwayScreen.newField(t)
          thing
        }
      }

      val fc: FieldContainer = NewFields
      fc
    }

    this.addFields(this.newFields)

    // Required because otherwise we will continue on to the "throwAwayScreen"s.
    override def isLastScreen = true
    override def nextScreen = Empty
  }
}