Thanks for all the information.
Yeah, it was either 10.7 or 10.8 that I pulled this off last time.
There is "StandardMenus.nib" in:
HD ▸ System ▸ Library ▸ Frameworks ▸ Carbon.framework ▸ Versions ▸ A ▸ Frameworks ▸ HIToolbox.framework ▸ Versions ▸ A ▸ Resources ▸ English.lproj
It seemed hopeful, but it seems like some things have changed in 10.10.
Previously I changed a system .nib to .xib, used Xcode to remove "All My Files" from the Finder top bar.
Alternatively, if anyone knows any other way to remove "All My Files" from the Finder bar, I'd be very happy.