location is /Users/YOURUSERNAME/Library/Application Support/Neutron

you can get there in this way:

open Terminal
cd "Library/Application Support"/
cd Neutron
nano Neutron.conf (than edit your conf file), save it with CTRL-X command

Mac OSX GUI version can be downloaded from: https://github.com/audiotopix/Neutron/releases

Apparently NODELIST is not necessary.

BTW: block synchronisation take really, really long time...