You can still do it, but you have to go to the parent folder and choose "Hide this parent...". I think it only works if the parent folder doesn't contain any images that have been imported to LR.
Not quite, Hal. 'Hide this parent...' will work whether the parent conatins images or not. However, if it does contain images then these will also be removed from the catalog. Fortunately, the user gets a warning about this (see screenshot). Whether they pay heed or understand the implications of the warning is another matter (i.e some don't).
Personally, I would just move the subfolder(s) with my OS file manager, and then tell LR where they are when it says it can't find them.