Lectora 11: how can I allow only one drop item on a drop zone

Hi,

we implemented a simple Drag and Drop question with three drag items and three drop targets, that now are called drop zones.

So

drag item one

drag item two

drag item three

and

drop zone one

drop zone two

drop zone three

In Lectora 11 it's now possible to place drop items one, two and three on drop zone one. And having drop items of similar size, the are placed on top or below of each other and it is difficult to see where the drop items went.

Is there a way to only allow one drop item in a drop zone?

Jan