So i discovered this when trying to remap keys.
You get kmac layout, kmini layout and kpad layout xml files with corresponding temphex files.
My initial action when editing source is to copy it and work on a copy... unfortunately kmacs.exe does not generate a temphex file, only a real hex file.
SO if you change the name of the layout xml file you won't be able to generate hex for it... so make a backup of both and edit the original