The only thing I changed in the config for gardens is the amount of drops you get from them. I just went back into the game and tried moving one using shift right click etc and didn't manage to get one to move. I'm wondering if you're thinking of something else as I'd have liked to be able to move them myself and went to the trouble of checking the config to see if there was a way to enable it.
Of course I could be thinking about the wrong type of garden as I assumed I was being asked about the gardens you get as rewards in the Taint Nutttin.
If you can get it to work, let me know as there's always a possibility I've missed something.
According to Pam's project page, you should be able to right-click them - https://minecraft.curseforge.com/projects/pams-harvestcraft/files/2221702 (fourth bullet on the 1.7.10d changelog) I've also looked through the 1.8, 1.9, and 1.10 pages, and other than a change in the types of gardens available, there doesn't seem to be any removal of this function.