In case you mess up the schema for any reason and you are no longer able to open the Gnome settings, e.g. gnome-control-center, just do the following and then logout and back in (or simply reboot):
rm .config/dconf/user
That’s it! Enjoy!
Sources:
https://www.linuxuprising.com/2019/03/how-to-reset-gnome-desktop-settings-to.html