Sorry I don't know the addon in deatail but here are some general ideas:
Normally the addons got some settings panel which you are able to reach from the main menu (press ESC and look for Addons / Settings).
There could be a button like "Free controls" or "Move controls" then.
Pressing this button again should fix the controls on the HUD then.
Another point could be a chat command you'll need to enter manually. Check the addon's description here if there are chat commands you can use to be able to move the controls around.
It really hasn't changed. There's no lock/unlock, you just switch to mouse mode and drag.
The hit box (for where you can click) can be a little finicky, so try dragging from a few different points if somewhere near the edge doesn't work.