This is turning out to be much more difficult than what I thought it would be.

I'm not finding anything on what to type in the en_US.xml file so I can compile it back to a .vkb file that will be usable.

Right now, clicking on the Tab key just types out the word Tab.

Probably not what you want here.

I emailed the author so maybe I'll hear back from him or perhaps someone else here can jump in and help.