I have not been able to create new folders in Elements 11. I have only been able to rename folders, not make new ones. In v7 & 9 it was easy, but not so in v11.
I find it quite easy to do this. All I do is go to:
File >> Watch Folders
Now a new window opens that allows you to ADD ... to create new folders. Click on the ADD button and then you get another window:
See this picture:
Hope this helps.
Please go to Folder tree view by clicking the small button next to "My Folders" label. You would see teh folder in tree hierarchy.
Now right click the parent folder and click "New Folder", just as shown.
Hope this helps!