You've always been able to call this yourself. You can manually call the ChildFormDialog.ShowDialog(...) and pass the parms. So that would be the workaround at the moment. However, we have exposed this in the next update. Here is the enhancement that has been added:
A new event argument parameter in the OnBeforeChildFormExecuted event called ChildFormParameters. By adding parms to this collection they will be passed on to the calling of the ChildFormDialog like this: ChildForm.ShowDialog(ChildFormParameters.ToArray()). This gives the developer the ultimate control in automation of a child form call through a ListView.