I did try finding the answer on my own first, btw :) For example I changed lineNumberWidth to 80, just to see what would happen. Nothing happened. To be sure I'm trying the latest changes, I'm installing to a "test" directory, using the '-i' and '-c' options, and uninstalling and re-installing after each code change.
https://github.com/geany/geany/blob/770cda40646e8ebfe6591df03356e2bcb71b875c...