"I've managed to find this snippet of code that lets me change my default file viewer from Finder to Forklift.

defaults write -g NSFileViewer -string com.binarynights.ForkLift-3; defaults write com.apple.LaunchServices/com.apple.launchservices.secure LSHandlers -array-add '{LSHandlerContentType="public.folder";LSHandlerRoleAll="com.binarynights.ForkLift-3";}'

I use Nimble Commander, and I think I can change to use NC by replacing com.binarynights.ForkLift-3

with whatever the corresponding program name for NC is."

"Find the .app file in Finder, then right click and choose “show package contents.” Inside of the folder called “contents” you should see a file named Info.plist. Open that with a text editor and find the line CFBundleIdentifier. The next should be something like X.Y.Z. You need to replace com.binarynights.ForkLift-3 in the command you posted with X.Y.Z"