How to add more drag objects in Drag and Drop Question

I have 5 drop target and 3 drag object. I tried to add 2 more drag objects, but they don’t appear in the selection panel for the drag-and-drop question, so they can’t be connected to the correct drop target.

Click “Insert Answer” to add a pair of drag-and-drop options in a drag-and-drop question. Then, delete the drag object or drop target as needed, as the drag-and-drop question only accepts the drag object or drop target inside it.

After insert and delete something