I have a similar problem with DO 10.0.1.0.4185.x64.
(0) OK, Here's my Library "Downloads". 'Incoming (E:)' is my save location for this Library.
(1) I start DO, left-click on Library "Downloads" in folder tree, right-click on the right side and select "New folder...", "New Folder" and OK.
(2) Then I double-click on "New Folder" (right side). After that my folder tree shows triple "New Folder" folders. If in first step 'Incoming (E:)' and 'Trillian (D:)' are expanded (as shown on "Triple-0.jpg"), double "New Folder" folders are displayed.