...you realized you can't drag'n'drop one List into another List.
Sure you can. In fact it happened and I spent that 30 mins undoing the mess that was created. My data definitely ended up in an existing list (I had to delete it from there after "Undo" did absolutely nothing).
All I wanted to do was drag'n'drop a newly created list, imported from a GDB file, into a newly created sub-folder. I tried numerous times and had it go into other lists, no list at all (data disappeared) and eventually where I wanted.
Maybe the issue was due to a slow PC but it was really frustrating. Fortunately I don't use BaseCamp much...