Backing up the interface

So I want to change my interface again and test it out for a bit, but want to be able to revert to what I'm currently using in case I decide I don't like the new layout. To do this, I need to be able to back up the settings, but I have no idea where it's stored.

The only big thing in the GW directory is gw.dat which I know can be deleted without affecting my layout.

I know about the restore defaults and undo changes buttons, but I'm not using the default and undo changes only works during that specific instance, which means I can't actually turn off the interface customization screen and try things out.

Snap a screenshot first so you have somthing to compare to if you want to put it back?

When you go to F11 and Interface just move stuff around as normal and if you don't like hit the undo button before closing options.