[GNC] Location of gtk css file on MacOS

[will at theprescotts.com]

I am running Gnucash 4.1.4 on MacOS 10.15.6 and I am looking for the location of the gtk.css file that is controlling the display. I have seen discussion of it here and have looked at the wiki but I am still having trouble.

I have files:
~/Library/Application Support/Gnucash/gtk-3.0.css
~/Library/Application Support/Gnucash/config/gtk-3.0.css

However, it doesn't look like Gnucash is reading or paying attention to either. If I run Gnucash in the gtk debugger with:

GTK_DEBUG=interactive /Applications/Gnucash/Gnucash-4.1.4/Gnucash.app/Contents/MacOS/Gnucash

It does appear to read the first one, but not when I run Gnucash normally (i.e. by double clicking on the Gnucash.app or from the command line).

Any suggestions?

Thanks,
Will