in Choose a Location CTV, impossible to drop a resource into an empty folder

I added a folder into a collection.

I went to a resource that I wanted to add into that empty folder.

I clicked "Add" which opened the Choose a Location dialog.

I dragged the resource and hovered over the folder. Because there's nothing in the folder, it won't expand, so I can't get a dotted line to appear, and hence cannot drop the resource into that folder.

Please let me know if you need more detailed ste-by-step on this.