Ah. So. . .
Well, I'm really not looking for things like this, honest, I'm just trying to secure my config (60 custom keys) through the UE's and reinstalls, etc. But in this build, under the 'My Documents' tree, in my ..\config\mykeys.xcfg file, I think the word should be theme, but is spelled 'thene=2' (above 'largeIcons=0'). So, 2 would correspond with 'default' in the 3 choices. -My setting.
I have no way of knowing if this matters to anyone, just hard not to make note of it, JIC. BTW, this folder full of config pairs saved me on one reinstall, as I had no Built-in copy.
For some reason it was empty the next time I needed it. Know what de-populates it? The uninstall didn't the first time.