The short answer is unfortunately No, not that way!
However, you can rename the recordings to have the exact same name, and the DVR+ will automatically create a "virtual" folder to put them in. This is exactly what the DVR+ does to all "series" recordings. You'll loose the show name, but the Info button can be used to see the description, and the date stamps remain unaltered.
I like your thinking!
Unfortunately, the DVR+ does not use Folders or Directories on the storage device for the recordings, it only uses disk partitions to separate the TS recordings from the binary data files, and each partition has one folder named "lost+found", in which I've never seen a file. The software sees recordings with the same name, and groups them in what appears to be Folders only in the DVR Recordings window (not on the EHD). Those "folders" are just "virtual", they're not real. If you do this, the DVR+ will still mount the EHD, will still show those recordings in the DVR Recordings window (the data are obtained from the binary data files, not the existence of recordings), but will NOT play them, issuing the message "Cannot start playback of this recording".
Actually, this is not untested! I already did this experiment, which is how I know what happens as I described above. But you're right, it's dangerous to mess around like that unless you take proper precautions, or you don't mind loosing everything. I highly recommend to anyone wanting to try things like this to first copy ALL files to the computer for safe keeping, and if something goes wrong (almost guaranteed), copy ALL files back to the proper partitions on the EHD.