The UI is defined in the executable file and the text displayed in the UI is defined by the msgstringtable.txt file. For example, old sakray executables have Equip and Stats windows separated, while newer RagRE executables have them merged. The only way to "modify" that is by hexing the executable file. You can look up the wiki about hexing : http://herc.ws/wiki/Hexing
thanks for this, i'll keep researching about it.