I haven't tried this, but you should be able to select the photo in the filmstrip at the bottom of the screen, and then drag it into the desired collection. (And if that doesn't work, then press G to go to the grid and it definitely works if you drag it from the grid, not from the filmstrip)
By the way, this is really a COPY and not a MOVE (for it to be a MOVE you would also have to delete it from the existing collection)
Duh! I don't know what I was thinking; thank you so much. Also, yes, I deleted the 'my new collection' collection afterward. Thank you!